It is now possible to report posts and comments

* cleaned javascript report view
* display status when the user send a report
* join the conditions of the inner ifs
* add a uniqueness constraint to the model
* differentiate between author is a local or a remote user
* simplify controller/mailer functions
* added missing action in report controller
* added the ability to disable report-email-notification
* using case instead of equal
* make report-type translatable
* using unless instead of 'if !'
* cleaned and optimized report model
* display validation errors to user
* joined if statements and removed duplicated code
* removed local variable in ReportMailer
* fixed put request for Report controller
* added diaspora copyright
* added report model spec
* renamed PostReport to Report
* added report button to SPV
* updated rspec

refs diaspora/diaspora#4732
refs diaspora/diaspora#4710
refs diaspora/diaspora#4711
refs diaspora/diaspora#4517