[BUILD] minor adaptions to the build system

 * removing the test_build related infos from the targets target
 * updated the pyOpenMS cmake to be a bit more OpenMS like
[DOC] removed test_build target from the documentation

 * incl. further cleanups related to the repo restructuring
Merge pull request #662 from aiche/feature/cmake-clean-ups

CMake and docu cleanups w.r.t. to the new layout
[BUILD,PYOPENMS] simplify pyOpenMS build system

- do not copy all files separately into build folder
- add gitignore statement
- add debug Python script to run Cython only on the pyx file
Merge pull request #661 from hroest/feature/pyOpenMSbuild

[BUILD,PYOPENMS] simplify pyOpenMS build system