Add Xflow WebCL image processing unit test
Add Xflow js platform tests
Add Xflow WebCL platform tests
Separate Xflow platform tests into fallback and targeted platform tests
Improve Xflow operator platform selection logic
Add an event listener in MatchTexture test
Fix false timeout problem in MatchTexture test
Fixed bug with async xflow operators.
Fix for issue #46. Correctly use an object map for opaque renderObjects.
Changes order in which asset data is overwritten.

When extending an assetdata or assetmesh, the data linked via
"includes" will override the data of the original entry.
Adapted asset pick filter to support filtering via classNames + test.
First steps towards assets within assets.
Several small fixes - first tests are working.
Several fixes for nested assets + handling of _postTransform assetdata entry.
Added new xflow.get operator used to extract array values by index.
Added match attribute to assetmesh.

The match attribute allows to override multiple assetmesh elements at the same time.
Adapted asset tests.
Started with tests for nested assets.
Finished tests for nested assets.
Merge branch 'instance-improved' into develop