Bump Rails to 3.2.19

Rails 3.2.19 fixes a possible SQL-Injection when using the PostgreSQL
adapter. However this is only exploitable when using the "bit" type,
which we don't.
Use double quotes when embeding translations in JS

Translations commonly include single quotes, which closes
the JavaScript string unexpectedly. Closes #5055
Port Getting Started page to Bootstrap
Merge pull request #5057 from blase/feature/4466-port-getting-started-page-to-bootstrap

Port Getting Started page to Bootstrap
Home page, registration page and robots.txt personnalization
Add my aspects link in the header
Add indication about testaccount and framasphere on the home page