Use absolute_root more consistently in Reshare

Closes #4956
It is now possible to report comments

* 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
Cleaned javascript report view
Display status when the user send a report
Diaspora review part 1

* 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

Podmin can see a extra checkbox in Settings > Account
for disabling 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
Changed report spec

* Removed ActiveRecord tests (that is handled in the controller spec)
* Added Mailer tests
* Added validation tests
Using save for report model

Instead of checking the status code I am using success and
error callbacks from model-save. In that case we have to return
json in the controller for signaling that the request was sucessfully.
Added destroy_reported_item to report model spec