Project search

*WIP*

Set a project search through: 
  - *Filters:* name, fields of study, student passions, team mode and session timeframe. 
  - *Sort:* A-Z, Recent, Oldest.
  - *Explore by:* Grid, List and map views.

To do:
  - Specs for projects (controller, model, acceptance).
  - Connect home search to project search.
  - Styles for ransack helpers, normal helpers are used.

Issues:
  - There's some kind of problem saving individual projects (team_mode: false).
  - Since *region* field is missing the filter is not defined yet.
  - Also since dates are handle in the *ProjectSession* model (which is currently located in another [branch] (https://github.com/ipoconnection/ipo-web/blob/dev/app/models/project_session.rb#L2)), the 'Session Timeframe' filter is temporarily working with *created_at* field.