Detect existing Geotrek install and exit if <0.21
Delete existing migrations and fake them on existing instance
Replace existing migrations with fresh ones, without language
Update DB columns of translated fields on languages setting change
Application available languages distinct from translated content (fixes #922)
Update changelog after migration reset (fixes #937)
Remove mention of italian in test fixtures (ref #922)
Merge branch 'reset_migrations' into develop

Conflicts:
	CHANGES
	install.sh