Make blob new and edit file editors more uniform

Created by: cirosantilli

DRY them up and make them uniform. UI changes:

• remove cancel button from file edit header: there is already a Cancel button the bottom of the page, which is the standard place for cancel buttons
• add branch to new file edit. Already present on the edit, so let's make it uniform.

After edit: no cancel:

Before edit:

After new (has branch on header):

Before new: