Introduces table for attachment list
Introduces asynchronous delete for attachments
Moves attachment destroy tests to specs
Fixes wiki page attachment destroy
Adds cuke for bug
Adds changelog entry

[skip ci]
simple refactoring for the reports: maybe this gets it below D
major refactoring of reports into separare classes

reports now live in separate classes: This brought up several issues
with buggy templates; lots of duplicate code has now been removed.

Still needs some view-testing, and maybe some unit-testing for the
service.
Worked in the review-remarks, added proper coypright notices where missing
abstract-class is ActiveRecord only, removing it.
added changelog-entry
limits principals returned by the autocompleter to only active or registerd
cleaning up unused code, rewriting scopes
updates changelog
adds a user pagination controller for timelines
removes scopes also present on the superclass
handles principals pagination controller same as users
moves pagination to api::v2
streamlines pagination specs, enables using index action
prevents timelines spec to change settings for following specs