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.
NEW: Created LessThanOrEqualFilter and GreaterThanEqualFilter
Added SSViewer::get_templates_by_class() to make the functionality in LeftAndMain::getTemplatesWithSuffix() more open.
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