Basic structure of extension for importing spatial data using GDAL/OGR

(references OpenFLUID/openfluid#6)
UI setup in extension for importing spatial data using GDAL/OGR

* Added UI design and behaviour
* Cleaned code

(references OpenFLUID/openfluid#6)
Threading in extension for importing spatial data using GDAL/OGR

* Added worker for fetching layers
* Added messages and progress bar while fetching layers

(references OpenFLUID/openfluid#6)
Cache system for remote layers in extension for importing spatial data
using GDAL/OGR

(references OpenFLUID/openfluid#6)
Adapt UI to geometry dimension of selected layer in extension for
importing spatial data using GDAL/OGR

(references OpenFLUID/openfluid#6)
Introduction of import structure in extension for importing spatial data
using GDAL/OGR

* Added precheck and import messages dialog
* Added structure for imported data
* Updated UI
* Cleaned code

(references OpenFLUID/openfluid#6)
Add of import precheck in extension for importing spatial data using
GDAL/OGR

(references OpenFLUID/openfluid#6)
Add of import system in extension for importing spatial data using
GDAL/OGR

* Added import worker
* Added automatic closing on successful import
* Cleaned code

(references OpenFLUID/openfluid#6)
Files copy and datastore in extension for importing spatial data using
GDAL/OGR

* Added copy of vector files in input dataset
* Added import in datastore
* Cleaned code in extension and map scene of spatial domain

(references OpenFLUID/openfluid#6)
Enhancements in extension for importing spatial data using GDAL/OGR

* Improved management of imported layers in datastore
* Fixed update of UI when switching between layers
* CLeaned code

(references OpenFLUID/openfluid#6)
Modify SELF_ID by OFLD_ID