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 logic will still attempt to find the `nupic-logging.conf` file using the old methods, in case the user has set `NTA_CONF_PATH` and provided their own logging config for some reason.