merge
fix url
added paste link to submissions, where paste is available
added before_create hook for setting paste_key
add paste_key to pastes and set pastekeys to all submissions, where paste available
added required logic for showing paste and no paste files
validation not really neccessary, as it is constraned in db
Added option to configure how pastes are visible and tested paste views

Merge branch 'master' of github.com:testmycode/tmc-server into nice

Conflicts:
	db/schema.rb
PR #138 minor cleanups.