Update doc needs libkrb5 dev

People who use the update guide should also install libkrb5-dev.

See merge request !1454

Add icon helper method

Use pry-rails gem instead of pry

Minor spec output cleanup

Improve calendar widget

See merge request !1453

Expose Link header in CORS Api calls

* cache user contributions for day
* ignore forks in calendar contribtuions

Refactor Repository to use new RepositoryCache class

Improvements to LDAP::User model

* method #changed? also tracks changes of identites (fixes issue with email mapping)
* find ldap identity before initialize one

Fixes #1946

See merge request !1452

* method #changed? also tracks changes of identites (fixes issue with email mapping)
* find ldap identity before initialize one

This outdated gem was the cause of those annoying MiniTest errors.

Also updates one use of `ensure_inclusion_of` which was deprecated in
favor of `validate_inclusion_of`.

This caused those random "true" outputs in the rspec output.

pry-rails has pry as a dependency and this lets us have all that pry
when we run `rails console` ❤

Abstracts away the lower-level implementation details from the
Repository model.

User contribution calendar via ajax

See merge request !1451

Bump GitLab for Docker to version 7.7.1

See merge request !321

Ability to clone project using oauth2 token

See merge request !1447

UX improvements (Implement lessons from user testing)

* add link to permissions help page from new project/group member form
* Improve UX for widget if merge request can not be merged
* Improve wording for fork project page

See merge request !1448

Small css improvements

See merge request !1450