Fix python wrapping bug.

The _opensim target needs the source output of the PyWrap target. There was a bug in the CMakeLists that caused the _opensim target not to depend on this source output unless CMake was re-run after PyWrap was build.

Also added a fix to get python wrapping working on APPLE Mac OS X, and improved error handling.
In java wrapping: fix bug, improve error handling.

1. Avoid using GLOB for osimJavaJNI target, as the _wrap.cxx files doesn't exist until after cmake configures.
2. Set up the JavaWrap target so it doesn't build each time CMake runs; it will only build when it is out of date.
Fix mistakes in Java wrapping CMake.

Added variable for the swig-generated header file. Added back the
explicit dependency on JavaWrap.
Fix CMake syntax error.

Clean up another CMake file. Remove _wrap.h from repository.
Add comment in Java wrapping cmake.
Update CoordinateAxis with Simbody's changes.

CoordinateAxis::assertIndexIsValid is gone in Simbody, but it still existed in
our copy of it that we use for SWIG.
Remove library dependencies from wrapping targets.

Previously, the swig source code generation targets depended on the libraries
being built. This slows down the build time, and is not actually correct: the
swig targets only depend on header files, not on compiled libraries.

So I removed these dependencies. The issue is then that if you edit a header
file, CMake won't know to re-run the SWIG targets. In this case, delete the
SWIG generated source code, and the swig target will re-run.
Merge pull request #97 from opensim-org/fix-wrapping-cmake

Fix wrapping cmake, addresses issues #41,  #97: Improves error handling for Python wrapping.
Attempts to fix an issue with building the wrapping on a mac, updates annotated SWIG headers so that wrapping builds successfully.