Introduce REST framework for Trek detail
Ugly fix for crash of DRF with concret inheritance
Migration of trek json detail
Migrated all JSON entries for Trek
Merge remote-tracking branch 'origin/develop' into trekking_json_view_migration

Conflicts:
	conf/buildout.cfg
Upgrade mapentity
Fix regressions
Start customizing POI JSON
Upgrade mapentity
Add more properties on POI JSON detail
Fix regression about trek parking
Fix trek detail test
Merge branch 'trekking_json_view_migration' into develop