(CDAP-369) Fix cdap-cli

* CLI now reads cdap-site.xml in the classpath for hostname/port/ssl configuration
* CLI now saves the generated access token to the local filesystem for later use
* cdap-cli.bat now passes arguments through to `CLIMain`
* cdap-cli.sh now passes arguments through to `CLIMain` and no longer `cd`'s into the CLI jar's directory 

Tested on Windows and Mac.
Probably better to call it .cdap.accesstoken.<hostname>