Issue-4769 - Unable to update case of label

Labels are saved in the database with the case they were originally created with.
Before this change if a user created a label with the same text but different case
the label would use the original case and no new label would be created in the
database. With this change, labels are now case-sensitive.

Steps to test:

1. Before this change, create a new issue with a new label "FIxMe"
2. Edit the issue and change the label to "FixMe"
3. Note that the label reverted to "FIxMe"
4. Apply this change
5. Edit the issue again and change the label to "FixMe"
Note that the new case was preserved. If you also look in the database in the "tags" table you will see that both labels are present - "FIxMe" and "FixMe".
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Add numbers.
Fix numbering by indenting.
More entries to changelog

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Look for project description during search

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Refactor search views

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Enable rack_attack by default.
Project#default_branch use repo HEAD instead of DB value now

Drop default_branch field from projects table
Use repository.root_ref as value for defautl_branch method
Fixes issue with default_branch and HEAD getting out of sync

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Replace assign with stub for default_branch

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Remove default_branch support from API project creation

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Fix spinach tests

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update CHANGELOG with default_branch changes

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Merge branch 'improve/default_branch' of /home/git/repositories/gitlab/gitlabhq
Require gitlab-shell 1.7.6

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Remove separate installation of charlock_holmes.
New API: create file in repo

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Specs for Create file API

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Improve message in email notifications
Removed Project#discover_default_branch since it not needed any more

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>