Send EmailsOnPush email when branch or tag is created or deleted.

Addresses #1951, #1957 and #1925.

![Screen_Shot_2015-03-17_at_13.58.15](https://dev.gitlab.org/gitlab/gitlabhq/uploads/16ff25adb4b4a7e1923612e0652442b4/Screen_Shot_2015-03-17_at_13.58.15.png)

![Screen_Shot_2015-03-17_at_13.58.22](https://dev.gitlab.org/gitlab/gitlabhq/uploads/e346c1d84aba3a093b722d0a4167e289/Screen_Shot_2015-03-17_at_13.58.22.png)

![Screen_Shot_2015-03-17_at_13.58.28](https://dev.gitlab.org/gitlab/gitlabhq/uploads/720437ecc13f317c6d20eff82ac60bd7/Screen_Shot_2015-03-17_at_13.58.28.png)

![Screen_Shot_2015-03-17_at_13.58.34](https://dev.gitlab.org/gitlab/gitlabhq/uploads/2b302bb6cdbe27c96a8dff1375236602/Screen_Shot_2015-03-17_at_13.58.34.png)

See merge request !1709

Don't show commit comment button when user is not signed in.

Address private issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2167.

See merge request !429

Conflicts:
	app/controllers/users_controller.rb

Replace commits calendar with contributions calendar

* count opening of issues and merge requests
* dont trigger git repository - use events from database
* count pushes instead of commits for faster and easier counting
* much-much faster since does not affected by repository size

See merge request !420

Fix #8966 Remove Milestones/Labels from project navbar when Issues disabled

Update views to single form of address. Change "my" to "your"

Part of user experience. Every software (twitter, facebook etc) talks to you like "change your password" but not "change my password".

cc @sytse @job

See merge request !1736