added model tests for the validation of birthdates #110
added translations for natural languages #100
Merge branch 'develop-ja' into develop-ja-localize-db
adjusted schema
Merge remote-tracking branch 'origin/develop-ja-bday-validation' into develop-ja

Conflicts:
	spec/models/user_spec.rb
added gem chronic for birthday validation, changed datepicker on students edit page to be 3 selects
added the user profile picture to the menu bar #58
added the folder structure and a missing.png for the chair #108
#82 Added validations and modified the tests in students_controller_spec accordingly
#82 Added Semester validation, made first/lastname immutable, made up student's edit view test
merged develop into develop-ha

conflicts:
user.rb
user_spec.rb
adapt job_offers form to ui_guidlines, #90, #111
redesigned students show #90, #111
updated schema.rb after migrations
Merge commit 'a97a641d3d2c7780f0e19ad52899774bf47e7b7b' into develop-js

Merge of develop branch without the commit causing authentication hickups in tests

Conflicts:
	app/models/student.rb
	spec/controllers/students_controller_spec.rb
	spec/factories/user_factory.rb
raise a not found error, if there is a user with the given id, but it's not a student.
adapted seeds for student field validations
refinement on students show #111, #90
added research assistant, only missing fields: chair, start date of work #79
adapt student show to guidelines, #111, #90