Move unit interface initialisation functions to its own file

This keeps import cycles from happening.

projects/common/classes/buttonElement.ts

 import { FontElement, SurfaceUIElement } from '../interfaces/UIElementInterfaces';
-import { initSurfaceElement, initFontElement, UIElement } from './uIElement';
+import { UIElement } from './uIElement';
+import { initFontElement, initSurfaceElement } from '../util/unit-interface-initializer';
 
 export class ButtonElement extends UIElement implements FontElement, SurfaceUIElement {
   label: string = 'Knopf';

projects/common/classes/checkboxElement.ts

-import { initSurfaceElement, initFontElement, InputElement, UIElement } from './uIElement';
+import { InputElement, UIElement } from './uIElement';
 import { FontElement, SurfaceUIElement } from '../interfaces/UIElementInterfaces';
+import { initFontElement, initSurfaceElement } from '../util/unit-interface-initializer';
 
 export class CheckboxElement extends InputElement implements FontElement, SurfaceUIElement {
   fontColor: string = 'black';

projects/common/classes/dropdownElement.ts

-import { initSurfaceElement, initFontElement, InputElement, UIElement } from './uIElement';
+import { InputElement, UIElement } from './uIElement';
 import { FontElement, SurfaceUIElement } from '../interfaces/UIElementInterfaces';
+import { initFontElement, initSurfaceElement } from '../util/unit-interface-initializer';
 
 export class DropdownElement extends InputElement implements FontElement, SurfaceUIElement {
   options: string[] = [];

projects/common/classes/radioButtonGroupElement.ts

-import { initSurfaceElement, initFontElement, InputElement, UIElement } from './uIElement';
+import { InputElement, UIElement } from './uIElement';
 import { FontElement, SurfaceUIElement } from '../interfaces/UIElementInterfaces';
+import { initFontElement, initSurfaceElement } from '../util/unit-interface-initializer';
 
 export class RadioButtonGroupElement extends InputElement implements FontElement, SurfaceUIElement {
   options: string[] = [];

projects/common/classes/textAreaElement.ts

 import { FontElement, SurfaceUIElement } from '../interfaces/UIElementInterfaces';
-import { initSurfaceElement, initFontElement, InputElement, UIElement } from './uIElement';
+import { InputElement, UIElement } from './uIElement';
+import { initFontElement, initSurfaceElement } from '../util/unit-interface-initializer';
 
 export class TextAreaElement extends InputElement implements FontElement, SurfaceUIElement {
   appearance: 'standard' | 'legacy' | 'fill' | 'outline' = 'outline';

projects/common/classes/textElement.ts

-import { initSurfaceElement, UIElement } from './uIElement';
+import { UIElement } from './uIElement';
 import { SurfaceUIElement } from '../interfaces/UIElementInterfaces';
+import { initSurfaceElement } from '../util/unit-interface-initializer';
 
 export class TextElement extends UIElement implements SurfaceUIElement {
   text: string = '<p>Lorem ipsum dolor sit amet</p>';

projects/common/classes/textFieldElement.ts

-import { initSurfaceElement, initFontElement, InputElement, UIElement } from './uIElement';
+import { InputElement, UIElement } from './uIElement';
 import { FontElement, SurfaceUIElement } from '../interfaces/UIElementInterfaces';
+import { initFontElement, initSurfaceElement } from '../util/unit-interface-initializer';
 
 export class TextFieldElement extends InputElement implements FontElement, SurfaceUIElement {
   appearance: 'standard' | 'legacy' | 'fill' | 'outline' = 'outline';

projects/common/classes/uIElement.ts

 // eslint-disable-next-line max-classes-per-file
-import { FontElement, SurfaceUIElement } from '../interfaces/UIElementInterfaces';
 import { IdService } from '../id.service';
 
 export abstract class UIElement {
@@ -54,20 +53,3 @@ export abstract class InputElement extends UIElement {
     this.requiredWarnMessage = serializedElement.requiredWarnMessage as string || 'Eingabe erforderlich';
   }
 }
-
-// ================================================
-
-export function initFontElement(): FontElement {
-  return {
-    fontColor: 'black',
-    font: 'Roboto',
-    fontSize: 18,
-    bold: false,
-    italic: false,
-    underline: false
-  };
-}
-
-export function initSurfaceElement(): SurfaceUIElement {
-  return { backgroundColor: 'lightgrey' };
-}

projects/common/util/unit-interface-initializer.ts

+import { FontElement, SurfaceUIElement } from '../interfaces/UIElementInterfaces';
+
+export function initFontElement(): FontElement {
+  return {
+    fontColor: 'black',
+    font: 'Roboto',
+    fontSize: 18,
+    bold: false,
+    italic: false,
+    underline: false
+  };
+}
+
+export function initSurfaceElement(): SurfaceUIElement {
+  return { backgroundColor: 'lightgrey' };
+}