API Remove Content-Length setting from HTTPResponse (fixes #8010)

This reverts commit 356a367eb5d05bea3dfa2edaeabc52a2496b93b2.
We can't use headers_sent() to determine an accurate
content length, since PHP defaults to buffering a couple of bytes
even without ob_start() (see "output_buffering" setting).
This makes the patch harmful, since it breaks any responses relying
on more structure data, like removing closing brackets from JSON.
Which in turn breaks the CMS in horrible ways (see #8010).
See #7574 for context.
API: Use HTMLText as default for RSS Description

To allow for custom RSS descriptions (i.e. provided by a method rather than a DB field) and avoid double escaping a better default class for Description is 'HTMLText'. http://www.silverstripe.org/customising-the-cms/show/11606#post319519
Consistently exposed ManyManyList information through getters.
FIX Node updates in IE without non-object error

Bug was most prominent after page publication,
which triggers a node reload. It iterated through
all node attributes to assign them to the existing node,
which apparently includes some non-scalar attributes
that can't simply be copied in IE.
Merge pull request #1123 from chillu/pulls/revert-content-length

API Remove Content-Length setting from HTTPResponse (fixes #8010)
Include "media" attr for module customCSS() (fixes #8219)
BUGFIX:fixed pagination for "upload from CMS" grid field pagination open/8085
FIX: Strict error warnings on DataExtension

PHP is throwing strict error warnings when overriding the
updateCMSFields and other functions in custom DataExtensions due to
the fact that the abstract class doesn't declare the variables should
be passed by reference
FIX: validate doesn't take var by reference

Got a bit carried away, validate doesn't take the var by reference
NEW Storing page preview states (fixes #8092)
Smaller styling for minor actions in CMS
Re-added 'auto' sizing for CMS preview

Regression from making sizes configurable via JS
Merge pull request #1156 from mandrew/patch-1

FIX: Strict error warnings on DataExtension
Merge pull request #1155 from silverstripe-rebelalliance/open8085

BUGFIX:fixed pagination for "upload from CMS" grid field pagination open...
FIX Don't escape values on TreeDropdownField readonly views

They typically output TreeTitle() which is assumed to be HTML.
Revert "FIX: Strict error warnings on DataExtension"
This reverts commit 1960df8bc30ecb0467a33275810fd121a0125733.

Revert "FIX: validate doesn't take var by reference"
This reverts commit 866bb0713b9918e0450a516da9b7662c3287e24f.

@ajshort has changed the method signatures in 1f6f7f08. While it wasn't explicitly noted in the commit message, I think its a good change - objects like a FieldList are always passed by reference in PHP, no need to declare that behaviour.
Move the shortcode docs to documentation, add examples.
Merge pull request #1157 from mateusz/shortcode-docs

Move the shortcode docs to documentation, add examples.
Loading "OR" in admin/assets for Chrome (fixes #8245)
Simplify sentence on shortcodes