support passing the site-packages directory on the cmake command line
support running tests when building inside the source tree on windows
install the header file for the rdkit inchi wrapper api

support compiling the postgres cartridge with inchi support when building against an existing rdkit installation.
replace backslashe chars in the path to the avalon source directory

some backslash characters in native windows paths are misunderstood by cmake as escape sequences.
Merge pull request #247 from rvianello/build_patches

build patches