Added IECoreNuke::SceneCacheReader
Added the SceneCacheReader for nuke versions > 7. The SceneCacheReader provides functionality to view, filter and display the geometry of SceneCacheFiles.
Concatenating transforms while rendering in sceneShape as opposed to computing the world matrix at each scene location.
Merge branch 'master' of https://github.com/ImageEngine/cortex
Merge pull request #48 from goddardl/sceneCacheReader

Added IECoreNuke::SceneCacheReader
Preventing crash when expanding a LinkedScene referencing a non-existant file.
Preventing crash when reading tags or links from standard nodes.
Fixed time dependency issue with ieSceneCacheTransforms.
Static state is now stored as a boost::tribool. This allows us to correctly set the time dependency flags during sceneChanged(), and detect when it is uninitialized during getParmTransform.
Fixed LinkedScene verification test.
LinkedScene started storing separate attributes rather than a compound. Updated the test, which required adding bindings for the various link attributes. Also renaimed timeAttribute to timeLinkAttribute as Lucio requested.
Fixed enabled state so it lasts across scene save/load
Merge pull request #53 from andrewkaufman/houdiniSceneRopCrashes

Houdini SceneCache Fixes
Disabling the GR_RenderHook for Houdini 12.5 or later.
Newer versions of Houdini will use a GUI_PrimitiveHook (not included in the commit).
Fixing test for Houdini 12.5
Temporarily disabling bound test for live scenes.
Houdini 12.5 introduced a bug in the HoudiniScene::readBound calculation. They have implemented a recursive bound calculation for OBJ_SubNets, but are not correctly transforming the child bounds. We have informed them of the error and will re-enable the test if they fix the problem.
Fixed PTCParticleReader build.

When we switched to specifying includes with -isystem in the CXXFLAGS, the configure check for pointcloud.h started failing, and we stopped building PTCParticleReader. This is fixed by using CheckCXXHeader which uses CXXFLAGS rather than CheckHeader, which doesn't.

Adding PTCParticleReader back into the build revealed another problem - it didn't implement the fairly recent pure virtual positionPrimVarName() method and therefore couldn't be instantiated, so this commit also implements that method.
Reduced use of GL matrix stack.

We were experiencing crashes in the Maya SceneShape, because it creates IECoreGL::Scenes with a much higher depth of nesting than is contained in the actual cache itself. This meant we ran off the end of the GL matrix stack with unfortunate consequences. The real long term solution is to stop using the GL stack entirely (it's deprecated) as documented in the comments, but this commit just avoids calling glPushMatrix() when the matrix is identity. Because the SceneShape creates a large number of identity transforms (at least one per cache level as far as I can see), this is quite effective.
Merge pull request #55 from johnhaddon/ptcParticleReaderFix

Fixed PTCParticleReader build.
Merge pull request #54 from andrewkaufman/houdini12.5Compatibility

Houdini 12.5 Compatibility
Merge pull request #56 from johnhaddon/matrixStackConservation

Reduced use of GL matrix stack.
Removed bogus include from Primitive.cpp.