Make cern a namespace package

If splitting the package (#30) and keeping the subpackages in the cern
namespace, we need cern to be a namespace package. Only then, multiple
independent modules can be installed into the same base package.
Move _checkCommand to cpymad.model._check_command

This function is only useful for this module. No need to keep it in a
separate location.
Move libmadx._madx_tools to cpymad

These functions are only used internally by cpymad.madx.
Remove pymad.globals and pymad.tools

This removes the global init() and get_pms() functions.
Remove obsolete packages from setup.py
Put TfsTable (etc) in cpymad.types

To make the cpymad package more independent from the rest of pymad.
Merge branch 'isolate-cpymad' into active-sequence

Conflicts:
	src/cern/cpymad/madx.py