FIX Director::is_absolute_url() now ignores query and fragment strings

Director::is_absolute_url() checks for //. It used to include the
entire URI, now it ignores the query and fragment strings.
BUG: Allow using instances for search filters.

Previously search filters could only be specified as strings, this
allows instances to be used so more complex filter configuration
can be used.
BUG Correct wrong parameter order.
FIX: use standard template rendering process for RSS feeds

This changes the behaviour of output to browser to use the standard SilverStripe rendering process rather than an echo statement to enable easier testability.
BUG: augmentSQL always extended on base data class on query finalization

The augmentSQL DataExtension method is always extended on the base data
class of data objects in DataQuery::getFinilisedQuery(). This results
in augmentSQL not being called for extensions that are applied to non-
base data classes when finalizing the query.

For example, if Versioned was applied to class B which extends class A,
which in turn extends DataObject, then augmentSQL would be extended for
class A in DataQuery::getFinilisedQuery(). Since class A doesn't have
the Versioned extension in this example, it would not work for class B.

Fixed this by extending augmentSQL on the actual data class and not
on the base class.
FIX 7742 Decode the URI encoded attribute before displaying it as the value for the tree dropdown
FIXED: Issue where urls with querystring arguments would not be properly concatenated with additional query parameters during ajax requests. The behaviour would not normally be noted except when using a module (such as Translatable) that adds parameters to data-url fields in forms.
FIXED: Issue where viewing an archived version of a page caused invalid SQL to be generated. This would only occur with subclasses of Page.
FIXED: Issue where versioned would join _versions tables on ID,Version instead of RecordID,Version
BUGFIX: Installer failed complaining about rewrite server-capability: XHR response was 3 chars long and therefore !== "OK"
MINOR: Added charset <meta> declaration to prevent errors cluttering up browser-based debugger console output
BUG More robust url comparison in CMS

Avoid ajax reloads when URLs differ in irrelevant ways,
e.g. admin/?locale=de vs. admin?locale=de.
This caused problems with the translatable module
reloading page content where it didn't need to,
because some previous robustness patches to the same problem
didn't apply (they only removed trailing slashes, ignoring
query parameter strings). The visible problem for this was
a broken tree panel, because it was ajax-loaded in parallel
with its container. Depending on ajax response order,
this would break the inner panel (in this case the tree),
since its original container was replaced with a new DOM.
Merge pull request #589 from simonwelsh/absolute_url

FIX Director::is_absolute_url() now ignores query string
ENHANCEMENT: Ntfcatn. image embedding(trac #7438)

Adding an additional warning / notification message, when author embedds an external image.
Fix TreeDropdownField toggle alignment in FF

See pull request #598
API Allow to force URL reload, while replacing the history state

Comes with a wrapper for easy reloading of the current panel.
Merge pull request #659 from ajshort/instance-search-filters

BUG: Allow using instances for search filters.
API Debug::showError() no longer calls exit() (fixes #2644)

Remove exit() from showError to continue execution after an user_error of warning (warningHandler) or notice (noticeHandler) level.
Merge pull request #666 from silverstripe-droptables/versioned-param-order

BUG Correct wrong parameter order.
Revert b9ed6f7f6d388fc451efbada2d1501d667322cb0.
Fix chosen dropdown width not being set.