Using pkg_resources to load local config files.

Fixes #1593. WIP. 

Includes moving nupic-default.xml and nupic-logging.conf into
nupic/support and loading them with pkg_resources. The default config
file is only loaded with pkg_resources if it is not found with the
NTA_CONF_PATH.
This was put here specifically for `nupic.regression`, but with the changes in this PR, it shouldn't be needed anymore.