Add send to mobile device function

[BishopGIS]

Add function to send vector/raster layer to mobile device. It seem to me, that this should be connected with nextgis.com account and special service, which will inform mobile devices about available geodata.
Also see here: nextgis/formbuilder#103
User connect mobile devices with nextgis mobile to it account. Mobile device periodically check if any data exist which can be loaded.