Version 0.5
* Allow not to download project and directly edit in PostgreSQL/Postgis,
* When project is downloaded offline, enforce to save it in `gis_data_home`
folder, and compute filename from project name in PostgreSQL. Thus do not ask
anymore user to select destination file. `gis_data_home` must be a QGIS global
variable referencing a valid folder. The reason for this is to allow local
filesystem layers in shared projects saved in PostgreSQL. Consequently, eash
user must have the same folder tree and the same common layers inside
`gis_data_home` folder,
* Before converting offline a project, if it is already loaded in QGIS, do not
load it again from PostgreSQL,
* bugfix: error when destination GeoPackage does not exists prior to
converting the project offline,
