ARROW-341: [Python] Move pyarrow's C++ code to the main C++ source tree, install libarrow_python and headers

[wesm]

This will enable third parties to link to libarrow_python.

For now, the pyarrow build system continues to use CMake -- for the purpose of resolving the thirdparty toolchain we may or may not want to go completely to distutils, but we can sort that out later.

[wesm]

One downside to this change is that the C++ libraries are now dependent on the Python interpreter version (see corresponding changes for Travis CI), similar to Boost.Python. I think the benefits outweigh the downsides, though.

[xhochy]

@wesm This definitely breaks the manylinux1 packages. Once this branch has a stable state, I would like to PR into this branch to get them working again. I'm a bit reluctant to add this to Travis as it would extend our build times even further.

[wesm]

This branch is stable -- I think you can go ahead with the fixes. I made best efforts to treat arrow_python like you are treating the rest of the library stack

[wesm]

Rebased

[wesm]

@xhochy the manylinux1 build is broken because of the multiarch changes f5157a0

-- Found the Arrow core library: /arrow-dist/lib64/libarrow.so
-- Found the Arrow IO library: /arrow-dist/lib64/libarrow_io.so
<SNIP>
make[2]: *** No rule to make target `/arrow-dist/lib/libarrow.so', needed by `build/release/libparquet.so'.  Stop.

This will have to get fixed in FindArrow.cmake in Parquet.

[wesm]

Suggest we merge this as is and fix up the build toolchain for manylinux1 in subsequent patches (I am happy to help, installed docker and just tried running the docker build)

[xhochy]

Ok, then let's continue first on the parquet-cpp side.

[xhochy]

+1, LGTM

[wesm]

Cool, merging, thank you