Define equality.

Very occasionally, unit tests would fail, because the parent of a model params object was not identical to a previously known model params object. I suspect that they were equal, just not identical due to falling out of the cache or similar.
Fixes #66.

The fix is simple, but I was scared that it might break other things. So far, it does not look like it. Once I get more unit test coverage, I'll sleep better.
Added test for issue #63.

This test currently fails because an allowed value is magically reduced.
Trying to work around what looks like a race condition.

In some cases, not always reproducible, there's a crash in -[GLLDocumentWindowController dealloc] in the unbind for the meshViewController, which somehow accesses the (non-existent, hence the crash) shader property on a GLLItem. This move increases several internal time limits to avoid that condition, and adds an autoreleasepool, so this crash can be localized more easily.