Showing a problem with SceneCache SOP loading a PointsPrimitive.

The points are doubling up on each cook, because they aren't linked to any Houdini primitive.
Removing code that wasn't doing anything
Adding a ParticleSystem in ToHoudiniPointsConverter
PointsPrimitive Uniform prim vars are now converted.

Since we have a ParticleSystem for each PointsPrimitive, we can support conversion of the Uniform prim vars to Houdini PrimAttribs.
SceneCache tagFilter supports SceneInterfaces with no tags
Testing HoudiniScene with flattened geometry.

Adding tests showing that it doesn't support flattened geometry (all in one SOP) unless every level of the hierarchy has its own shape.
Testing SceneCache ROP for flattened geometry.

Adding test showing that it doesn't work for flattened geometry, because the HoudiniScene is returning the wrong results.
Fixed HoudiniScene bugs for flattened geometry.

Gaps in the hierarchy are now supported, and this commit fixes the tests from the previous two commits.
Added support for ri:areaLight parameter to IECoreRI::RenderImplementation::light
Merge pull request #93 from andrewkaufman/pointsInScc

SceneCache SOP loading PointsPrimitives
Merge pull request #94 from andrewkaufman/emptyTags

SceneCache OBJ tagFilter supports SceneInterfaces with no tags
Merge pull request #95 from andrewkaufman/houdiniSceneFlatGeoBug

SceneCache ROP flattened geometry bug
Adding HoudiniScene::node().
Fixing constness of scene() method.

Also preventing bad calls if the necessary parameters don't exist. This avoids ugly error messages when dealing with broken nodes.
Adding ForceObjects parameter to the ROP.

This allows users to force specific objects to expand (and force the unlisted objects to be links if possible). An empty value will behave as normal (no forced behaviour).
Merge pull request #97 from andrewkaufman/ropLinkControl

ForceObjects parameter for SceneCache ROP
Updating Changes for a16
Fixing comments
Fixed bug when loading CoordinateSystems in Houdini.

It had been trying to access the local transform, which may or may not exist.
Merge pull request #96 from danieldresser/addAreaLightRi

Added support for ri:areaLight parameter to IECoreRI