It is now possible to report posts and comments

- [x] It's not possible to report comment
- [x] The e-mail received by the podmin should contain a link to /post_report
- [x] Podmin should be able to disable report-email-notification for his account
- [x] There is no confirmation when the user validates the pop up with the indication why he reports the post
- [x] The report is sent even if the user cancel (see #4720)
- [x] Renamed PostReport to Report
- [x] Added report button to SPV
- [x] Need some tests for SPV
- [x] Updated rspec for the controller
- [x] Clean-up the javascript backbone stuff !! (appreciate any help ;)
- [x] you can report post and comment in SPV

refs diaspora/diaspora#4732
refs diaspora/diaspora#4710
refs diaspora/diaspora#4711
refs diaspora/diaspora#4517

- Q: The e-mail received by the podmin should contain the reason given by the user