In java wrapping: fix bug, improve 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 Set up the JavaWrap target so it doesn't build each time CMake runs; it will only build when it is out of date.
opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core