Merge pull request #6526 from PerJensen/master

fix(css): prevent stretching images in IE8
feature(externalpages): page layout changed to one_column

fixes #6535
fix(pages): memory leaks in large page trees

Uses ElggBatch to avoid memory leaks in large page trees, fixes $container type check

Fixes #6477
Merge pull request #6480 from hypeJunction/pages-fixes

fix(pages): use ElggBatch to avoid memory leaks
Merge pull request #6537 from jdalsem/externalpages-layout

feature(externalpages): page layout changed to one_column
fix(hooks): return values defaults to null in javascript

Fixes #6499
fix(hooks): handlers returning null/undefined don't change returnvalue in javascript

Fixes #6531
Merge pull request #6532 from sembrestels/js-hooks-fixes

Normalizes the JavaScript elgg.trigger_hook to behave like PHP's
feature(uservalidationbyemail): forwarding to an info page after registration

Replaced system message by an informative page.
Removed system message when users try to log in, there is already another
message explaining why they can't log in.

Fixes #6247
Merge pull request #6514 from sembrestels/uservalidationbyemail-infopage

User validation by email info page
fix(admin): fixed javascript error on toggle simple cache checkbox

Fixes #6529
Merge pull request #6550 from sembrestels/admin-js-fix

fix(admin): fixed javascript error on toggle simple cache checkbox