AssetLocationPlugin instances now define which of the asset locations
they provide are seed asset locations, and AbstractBundlableNode has now
been modified to use this method.
Renamed SeedLocator to IndexPageSeedLocator since that is all it is used
for.
BundlableNode.getSeedAssets() renamed to
BundlableNode.modelSeedAssets(), and necesarry changes made so that it
no longer has any reliance on any of the plug-ins.
Added TODO to remove model dependency on plug-in code.
WorkbenchResourcesAssetLocation now determines the seed assets using the
model, rather than being tied directly to our BRJS conformant asset
location plug-in.
Added some TODOs for another area where the model is dependent on
plug-in code.
Merge pull request #625 from BladeRunnerJS/define-seed-asset-locations-within-plugin

Define seed asset locations within plugin