Add json_expressions testing gem to simplify testing of complex json
Get submission details API
Merge remote-tracking branch 'upstream/master' into submissions_editing_api

Conflicts:
	Gemfile
	lib/app.rb
Fix indention - use 2 spaces in view and test
Fix tests and remove nit comments
Add additional fields after merge
Merge pull request #477 from Maxim-Filimonov/submissions_editing_api

Internal API structure