Issue #19296 - Cleanup old unused code/files and consolidate

This pull request will change node-datasource to only use XM.SimpleModel.
We can now cleanup the old XT code which this pull request does.

Once this has been merged, you will need to make some changes to your server.

1. Review changes to sample_config.js file and update your local config.js file to match. Several setting hard coded into main.js have been moved here:
> https://github.com/bendiy/xtuple/blob/19296/node-datasource/sample_config.js

2. You may need to remove all active sessions from your database because the session secret is now stored in xtuple/node-datasource/lib/private/salt.txt
> DELETE FROM xt.sessionstore;

3. All npm package installs have been consolidated to xtuple/node_modules.  You need to delete your old node_modues directories:
> cd xtuple/node-datasource
> rm -rf node_modules
> cd xtuple/node-datasource/xt
> rm -rf node_modules
> cd xtuple/lib/backbone-x
> rm -rf node_modules

4. Then install all npm packages which appears to require sudo now:
> cd xtuple
> sudo npm install

The salt.txt file is currently under revision control.  Should it be removed?
> https://github.com/xtuple/xtuple/blob/master/node-datasource/lib/private/salt.txt

I found the cause of file permissions changing from 664 to 775.  If you are using SAMBA to access source code, you need to make this change to your /etc/samba/smb.conf file.
> http://stackoverflow.com/a/13020343/251019

Then be sure to restart SAMBA:
> sudo service smbd restart
> sudo service nmbd restart

All file permissions have been cleaned up in this pull request.