First successful "new Topic" creation. Yeah! Misc optimizations.

* we can now create new Topics. They have a "virtual" property "content", which is used only to create the Topic's first Post. It is unset before Topic saving.
* our Forums & Topics DB tables "name" columns have been renamed to "title" for more consistency
* added a quick'n'dirty "SQL migrations concatenation" CLI script
* CSRF hidden <inputs> are now factorized in a common Twig file
* misc optimizations and bugfixes here and there
Twitter Bootstrap test theme: switched from Grunt to gulp, better assets management

+ fixed quotes style on our app gulpfile
"ugly JS code" TODO comment removed from "ajax-navigation" core Plugin config file
Added a "Ajax content loading" visual indication