Added btStaticGroundShape interface.

I have built it locally and written a small example to confirm it works. I am not sure how to get the automated tests working. When I run python test.py in the root dir I get the following error:
0 : regression tests
      basics.js
Traceback (most recent call last):
  File "test.py", line 38, in <module>
    output = run(fullname)
  File "test.py", line 21, in run
    return Popen(JS_ENGINE + ['-e', 'gcparam("maxBytes", 1024*1024*1024); load("' + build + '"); load("' + os.path.join('tests', 'testutils.js') + '")', filename], stdout=PIPE).communicate()[0]
TypeError: cannot concatenate 'str' and 'list' objects.