feature(file): display file upload limit on file upload form

Refs #6355
fix(upgrade): Corrects query to clear admin remember me cookies
Merge pull request #6773 from mrclay/fix_clear_codes

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
Merge pull request #6781 from ewinslow/docs-contribute-code

docs(contribute): clean up PR instructions
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
Merge pull request #6794 from ewinslow/deprecate-b6785

chore(travis): add 'deprecate' commit type
Merge pull request #6790 from jdalsem/page-menu-collapse-css-fix

Page menu collapse css fixes
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
Merge pull request #6788 from jdalsem/plugin-text-file-sidebar-menu

fix(admin): show plugin settings menu on markdown page
Merge pull request #6789 from jeabakker/enable-site-notifications

chore(upgrade): enable site_notifications
Merge pull request #6791 from jeabakker/elgg-http-request-magic-quotes-gpc

fix(core): no longer strip slashes on $_FILES and $_SERVER
docs(changelog): Move CHANGES.txt to CHANGELOG.md
docs(changelog): Better markdown formatting