python: make 'python' install everything instead of just the interpretter

Follow the python3 behaviour, and common sense, by making 'python' install
python-modules instead of python-core.  This means a user installing python gets
all of Python, instead of just a fraction of the library.

[ YOCTO #13402 ]

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>