Created layer storage : use geopackage file instead of $HOME/.q4ts directory

When creating layers with Q4TS GUI, layer are always stored in $HOME/.q4ts directory. Filename is not defined by user and when we want to copy current project to a different directory we must check layer filename one by one and copy the files to create a new QGIS project.

This behavior must be changed and all layers created from Q4TS GUI should be saved in a single geopackage. The geopackage used must be defined in QGIS project settings.

When user ask for layer creation :

• check if a geopackage is defined in QGIS project
• if not ask user to define geopackage path and project name and save current QGIS project the created geopackage
• add new layer in the previously defined geopackage