[WIP] Reduce number of queries when loading home page

[tonio]

What still needs to be done:

• Fix broken tests (problem loading translations in fixtures)
• Check performances on larger data set

[tonio]

.get(project.id) isn’t used here cause it causes to be loaded from the Session and not from database, ending in translations not loaded.

[pgiraud]

It's broken for now :

• searching for a word gives wrong results,
• searching for "your projects" is super slow and doesn't give good results.