timeseries.py TimeSeriesSource changed staticmethods to classmethods which allows to inherit the TimeSeriesSource object

Signed-off-by: Benjamin Jakimow benjamin.jakimow@geo.hu-berlin.de <benjamin.jakimow@geo.hu-berlin.de>

log messages contain failed input sources
refactoring dateparser.py
timeseries.py - sensorID contains source-specific sensor/product name

Signed-off-by: benjamin.jakimow <benjamin.jakimow@geo.hu-berlin.de>

changed calls for gdal.Dataset source path from dataset.GetFileList()[0] to dataset.GetDescription() (should be faster and hides irrelevant errors related to image pyramids)
timeseries.py:
- asynchrone loading of source images based on QgsTaskManager (doLoadTimeSeriesSourcesTask, addSourcesAsync)
- TimeSeriesSource dates can be more precices that the related TimeSeriesDatum

Signed-off-by: benjamin.jakimow <benjamin.jakimow@geo.hu-berlin.de>

fixed bug in vector layer visualization
pulled qps updates

added WCS support
added TimeSeriesDataSource
allows to use multiple source per TSD

fixed DTG parsing from ENVI header
recognizes YYYY as date

added # -*- coding: uft-8 -*-   and  # noinspection PyPep8Naming to each module
added GPL License statement to each module
added from __future__ import absolute_import to each module

improved QGIS interaction
several UI issues and smaler bugs fixed

added ImageDateParserSentinel2

class ImageDateParser to be inherited by data-set specific date-time-group parsers
class ImageDataParserLandsat(ImageDateParser) to extract date-time-groups from Landsat like data-sets (SceneID / ProductID)