Started creation of standard website pages

- All website functionality must be done in standard pages before any
  other addition in the desktop system
- Added sign-in and sign-up system with Spring Security
- Added schools base operations (CRUD operations with authority check)
- Removed Foundation framework for Twitter Bootstrap framework
- Removed old useless files ("old_XXX")
- Removed unused files
  -> Desktop JSP pages, since DOM elements are auto-generated by
     Javascript
- Started implementation of full school managment system
Continuation of standard pages implementation

- Added prototypes pages with Boostrap and JQuery updates through Ajax
  -> Way more dynamic than simple requests, but their implementation is
     ignored for the moment for simplificiation
- Added an Ajax controller to handle Ajax requests
  -> Jackson API is used for JSON responses
  -> Not used yet: Ajax implementation is ignored for the moment
- Modified almost all existing controller to allow pagination in lists
- Added a "findRangeWithXXX" method to almost all DAOs for pagination
  purpose, where XXX is the entity "container"
  -> E.g.: a school contains N trainings, N modules
  -> Also modified all related services classes
- Modified "build.gradle" to add Jackson and Jackson-Hibernate
  dependencies
- Added some Spring handler interceptors
  -> Used for general data fetching and checking
  -> E.g.: every URL with /schools/{schoolPk} need to fetch and check for
     the school with the schoolPk primary key
- Added JQueryUI and CKEditor dependencies for slide creation purpose
  -> JQueryUI for the "sortable" API
  -> CKEditor for the WYSIWYG editor
- Updated almost all "view" and "list" views of the web application for
  clarity