BUG onDemand plugin fixture

Added trim() to decodePath function. Headers X-Include-* comes with a
space so some files are loaded twice. Looks like that depends on a
webserver. nginx has the space.
Check if remote class exists in DataObject->getRemoteJoinField()
NEW: Created LessThanOrEqualFilter and GreaterThanEqualFilter
Added SSViewer::get_templates_by_class() to make the functionality in LeftAndMain::getTemplatesWithSuffix() more open.
Merge query strings in $.path rather than duplicating

Fixes common duplications like ?locale=en_US&locale=en_US,
triggered e.g. by gridfield's showDetailView().

See https://github.com/silverstripe/silverstripe-translatable/issues/154
Merge pull request #2708 from chillu/pulls/addsearchparams

Merge query strings in $.path rather than duplicating
Added .content styles to debug.css, removed fieldset styling
Leave original ValidationException intact in write()

If we want DataObject->validate() to be used instead of
the form layer, we should allow for validation errors
to be passed through unchanged to the controller layer
so we can present them to the user. The context of
which class is written should be apparent from the stacktrace
of the exception.
Merge pull request #2714 from chillu/pulls/validate-write-message

Leave original ValidationException intact in write()
Merge pull request #2679 from micmania1/2658-get-templates-with-suffix

API: moved getTemplatesWithSuffix functionality out into a SSViewer
Removed debug code
Added index docs to DataObject

Thanks to @oddnoc for getting this started, see
https://github.com/silverstripe/silverstripe-framework/pull/2686
Merge pull request #2622 from froog/patch-1

Created LessThanOrEqualFilter and GreaterThanEqualFilter
Merge pull request #2615 from a2nt/jquery.ondemand-fix

BUG onDemand plugin fixture
FIX Check for file in project() folder when calling Requirements::themedCSS() #2613

Allows overriding of theme and module css files by looking in project() folder first. Consistent with documented behavior.
FIX: Year.php getDefaultOptions now fixed, sets key as year. Also added YearTest unit test.
Update SQLQuery.php

Updated `SQLQuery` class code examples for functions `setOrderBy` and `addOrderBy` to use their new names.
Merge pull request #2727 from jaydenseric/patch-1

Fixed `SQLQuery` class code examples
Clarify usage of extend within DataExtensions
beforeMemberLoggedIn/beforeMemberLoggedOut hooks

Required to save/restore parts of the session information,
which Member nukes indiscriminately on logout.

Specific use case is restoring linkages to temporary databases
on Behat test runs.