Handle multiple databases

[mduplouy]

Feature was requested by @marsender

It works well now on the front part (I added a new param to almost all urls)

What is still missing :

• Front office :
  • Add a selector to easily select which db to use (for new it must be changed in the url)
• Generate thumbnail command :
  • Either select a db or run the processing on any configured db
• Back office :
  • Select on which db to run the trigger stuff
  • Think about a database specific permission management

[mduplouy]

Features is ok for now (database change on front, triggers per database on back)