Use CMake's ExternalProject to fetch and build googletest.
Don't clobber any CXX_FLAGS from the environment.
Compile test schemas out-of-source.
Add missing target for 'capnpc-capnp'.
Support installing with CMake.
Specify/fix library dependencies.
Add 'FindCapnProto' CMake module to locate libraries and compile schemas.
Support disabling builds of the command-line tools and unit tests, and using an external compiler.
Merge pull request #128 from pqu/cmake

CMake improvements