* Pull request options migration and UI in settings

* Add ignore whitespace functionality

* Fix settings if pull requests are disabled

* Fix migration transaction

* Merge with Rebase functionality

* UI changes and related functionality for pull request merging button

* Implement squash functionality

* Fix rebase merging

* Fix pull request merge tests

* Add squash and rebase tests

* Fix API method to reuse default message functions

* Some refactoring and small fixes

* Remove more hardcoded values from tests

* Remove unneeded check from API method

* Fix variable name and comment typo

* Fix reset commit count after PR merge

* Integration test for activity page

* Small code refactoring for acitvity page

* Move activity stats calculation logic to model

* Fix so that user can still fork his own repository to his organizations

* Fix to only use owned organizations

* Add integration test for forking own repository to owned organization

* Helper functions for intergration test boilerplate

Set request headers in helper functions, and new helper for requests with string-formatted URLs

* Make branch deletion URL more like GitHub's, fixes #1397

* Add PR branch deletion integration test

* Do not allow deleting protected branch

* Change http error code to 403 if user has no write rights to repository

* Add check to not panic if forked repository has alrady been deleted

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>