Add application form

this is a first proposal of an application form and a base for discussion on #61 

missing:
 - [x] add links to resources and information
 - [ ] styling
 - [x] better and clearer wording 
 - [x] are those the fields we need?
 - [x] infos

anything else missing?

the current state can be seen on: http://rgsoc-teams-staging.herokuapp.com/