Use css grid instead of flex plus calculating margins in template

Using the html property "disabled" results in a warning message in the
player when reactive forms are used at the same time.

Fix import order

Use the same settings as in simple drop list

ViewEncapsulation.None is required for overriding tooltip

DragNDropValueObject no longer has the stringValue property
but a TextLabel with text

# Conflicts:
#	projects/common/models/elements/compound-elements/cloze/cloze-child-elements/drop-list-simple.ts
#	projects/common/models/elements/compound-elements/cloze/cloze-child-elements/text-field-simple.ts
#	projects/common/models/elements/compound-elements/cloze/cloze-child-elements/toggle-button.ts
#	projects/common/models/elements/compound-elements/likert/likert-row.ts
#	projects/common/models/elements/element.ts
#	projects/common/models/elements/input-elements/checkbox.ts
#	projects/common/models/elements/input-elements/drop-list.ts
#	projects/common/models/elements/input-elements/dropdown.ts
#	projects/common/models/elements/input-elements/radio-button-group-complex.ts
#	projects/common/models/elements/input-elements/radio-button-group.ts
#	projects/common/models/elements/input-elements/slider.ts
#	projects/common/models/elements/input-elements/spell-correct.ts
#	projects/common/models/elements/input-elements/text-area.ts
#	projects/common/models/elements/input-elements/text-field.ts
#	projects/common/models/elements/text/text.ts
#	projects/common/models/section.ts
#	projects/editor/src/app/services/verona-api.service.ts

This button helps the user to detect if a page has additional,
hidden content

DragAndDropValueObjects are now a sub-interface of TextImageLabel, which 
requires a set imgSrc and imgPosition property. (The reason is that the 
editor needs a way of generating Labels therefore needs the imgSrc set 
to something else but undefined.)

- Replace asynchronous child processes with synchronous processes
- Add shortcuts to package.json

- Refactor subscriptions for verona commands

Aslo create new props panel component and move border stylings to 
separate fieldset (wihtin the styling tab).

#291

One as a general label above the table and one for the first column 
heading.

Since this is no proper InputElement separate properties panel inputs 
are used.

#272

To be the same as with Material inputs.

#319

Add new parameter 'itemsPerRow'. This limits the grid columns used, 
making items move to the next row if overextending.

Also simplify component structure.