Api authentication interceptor and login service

Adds service that are needed for #15 to be implemented.
bowerInstall generates this line, and will give us issues. It's been sorted in the clients branch: https://github.com/jembi/openhim-console/blob/clients/Gruntfile.js#L150

Maybe we should cherrypick that commit? Or I can try getting the last things sorted, then we can merge that branch and you can pull in the changes?