Move wrapped C library to subpackage

Move wrapped C library to subpackage

Create new subpackage rmr/rmrclib with the C library loaded via ctypes.
Add method to get constants from RMR library and detect mock objects.
Split test files into test_rmr and test_rmrclib.
Extend sphinx configuration to mock the rmrclib subpackage, so the
rmr package receives a mock instead of a real object.
This change allows generation of API documentation by Sphinx
when the .so file is not available and import fails, for example
at ReadTheDocs.

Signed-off-by: Lott, Christopher (cl778h) <cl778h@att.com>
Change-Id: Idb9bb1d7a534c4142ea0353b5a48d3132e55f6e6