Support cloning reports

[lippserd]

resolves #45

[nilmerg]

Rebased. Fixed conflicts. Though, I don't merge it because:

• If the name isn't changed, it silently does nothing
• If the form autosubmits, the tab label changes to New Report
• If pushing the refresh button after the form autosubmitted, the report details get lost

The form needs its own endpoint. For the name validation anyway.