PLD: hide all the modal children before showing the selected one, closes #563
PLD: indentation and helper to check file validity
PLD: test that invalid file is caught, #563
PLD: check for blank file value in JS, closes #519
RR: set indentation to two spaces
Merge pull request #564 from onaio/563-add-form-broken

project model and file checks closes #519 and #563