Merge branch '1.9' into 1.x

Conflicts:
	.travis.yml
	CONTRIBUTING.md
	INSTALL.txt
	composer.json
	docs/appendix/faqs.rst
	docs/guides/hooks-list.rst
	docs/guides/upgrading.rst
	docs/guides/views.rst
	docs/guides/widgets.rst
	docs/intro/index.rst
	docs/locale/ca/LC_MESSAGES/index.mo
	docs/locale/de/LC_MESSAGES/about.mo
	docs/locale/es/LC_MESSAGES/about.mo
	docs/locale/es/LC_MESSAGES/appendix.mo
	docs/locale/es/LC_MESSAGES/intro.mo
	docs/locale/fr/LC_MESSAGES/about.mo
	docs/locale/it/LC_MESSAGES/about.mo
	docs/locale/ru/LC_MESSAGES/about.mo
	engine/classes/ElggDiskFilestore.php
	engine/classes/ElggPlugin.php
	engine/lib/elgglib.php
	engine/lib/input.php
	views/default/output/tags.php