fix(css): add hover classes to hover icons

Fixes #6737
fix(upgrade): Corrects query to clear admin remember me cookies
docs(contribute): clean up PR instructions
docs(contribute): add instructions for rewriting commit messages

Refs #5976
chore(upgrade): enable site_notifications

when upgrading from elgg 1.8 to elgg 1.9 the site_notifications plugin
takes over the 'site' notification from the messages plugin. So enable
this new plugin if the messages plugin was enabled

Fixes #6468
chore(css): changed page menu item radius 

It is now in line with other rounded navigation elements
fix(css): selected page menu does not collapse sub menu
chore(travis): add 'deprecate' commit type

This type will allow us to easily call out deprecations in changelogs

Fixes #6785
fix(core): no longer strip slashes on $_FILES and $_SERVER

When magic_quotes_gpc is enabled on your server file uploads would fail.

The Elgg_HTTP_Request class should only undo the magic quotes on the GPC
(GET, POST and COOKIES) super global not on other super globals (SERVER
and FILES)

Fixes #6777
feature(core): better registration of usersettings handlers

This will allow plugin developers to replace specific parts of the user
settings action without redoing part of the core actions.
fix(admin): show plugin settings menu on markdown page
docs(changelog): Move CHANGES.txt to CHANGELOG.md
docs(changelog): Better markdown formatting
docs(changelog): Fully updated CHANGELOG.md (to 1.9.0-dev)

Fixes #5798
chore(composer): pull version from composer.json

This would allow us to use grunt-bump to increase version numbers
programmatically to reduce release-process overhead.

Also opens to the door to install Elgg with composer:

```
composer create-project elgg/elgg ./path/to/elgg
```

Refs #6288
chore(release): conventional-changelog support

Refs #6783
chore(docs): Make toctrees only one level and correct several typos

Refs #6799
docs(contribute): add instructions for translators
chore(release): Add .mailmap to canonicalize contributors
fix(groups): Run discussion reply migration regardless if groups plugin is enabled.

This upgrade must be run even if the groups plugin is disabled because the
script will be removed in Elgg 1.10 and we don't want anyone to get stuck
with old annotation replies just because the groups plugin was not enabled
when site was upgraded from 1.8.

Fixes #6729