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

Refs #6355
fix(core): prevents upgrade scripts from attempting to create the same ElggUpgrade more than once

Attempting to create two ElggUpgrade objects with the same URL causes a fatal error. Now the
scripts check whether the ElggUpgrade already exists.

Fixes #6824
Merge pull request #6831 from juho-jaakkola/issue_6824

Prevents upgrade scripts from attempting to create the same ElggUpgrade more than once
Revert "chore(amd): added tests for AMD module registering and loading"

This reverts commit 89ed983f5b7d0190d76f838742dc571bcd72936d.
Revert "fix(amd): removed elgg_require_js for backwards compatibility"

This reverts commit 76584089bee2b3246c736edb6b250e149acf906f.

Conflicts:
	engine/lib/views.php
Revert "Fixes #5090: Possible to register js as shimmed AMD module"

This reverts commit 4dcaf3889c1800ea879db1606f7883a21edf3a6f.

Conflicts:
	engine/classes/Elgg/AmdConfig.php
	engine/tests/phpunit/Elgg/Amd/ConfigTest.php
fix(js): Separated elgg_load_js() and elgg_define_js().

Refs #6603, #6497, #5090.
docs(amd): Separated design and guides for AMD docs.

Refs #6603, #6497, #5090.
Merge pull request #6782 from brettp/revert_6497

Revert 6497
fix(aalborg_theme): only pass body_attrs if they are set

Follow-up of #6479
chore(travis): Switched to blacklisting not-tested branches instead of whitelisting

For details see: http://docs.travis-ci.com/user/build-configuration/#Specify-branches-to-build

Fixes: #6851
chore(composer): Added validation of composer.json and necessary fields to pass validation
Merge pull request #6853 from Srokap/ticket_6851

chore(travis): Switched to blacklisting not-tested branches instead of whitelisting
Merge pull request #6854 from Srokap/composer_validate

chore(composer): Added validation of composer.json and necessary fields to pass validation
chore(release): Improved version control in release script as well as error handling.

Fixes: #6850
Merge pull request #6847 from Srokap/semver_branches

chore(release): Improved version control in release script as well as error handling.
fix(UserPicker): no messages in userpicker due to lack of i18n

default elgg autocomplete disabled the messages in jquery autocomplete,
this now also applies to the UserPicker
chore(release): v1.9.0-rc.1
Merge pull request #6860 from beck24/release-1.9.0-rc.1

chore(release): v1.9.0-rc.1
fix(deprecated): Corrected invalid deprecation notice and added more details to few others

Fixes #6869