Make installable using Python distutils
Use installed planex executables in build system

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>
Move paths into globally accessible module

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>
Build packages within current working directory

Build everything in ./planex-build-root within the current working directory.

This means that for the directory of specs, they can now built using the
installed python modules (planex-configure, planex-build)...

$ planex-configure .
$ planex-build

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>