Fixes to bugSplit.js script

* Made the script directly executable.

* Create a directory for the bug report files based on bug data
  and move the bug report and all files into that directory so
  that each bug is self-contained making it possible to process
  multiple bug report files without worrying about stepping on
  each other.

* Strip content upto <body> and after </body> from originalHtml
  since editedHtml doesn't have these tags.

Change-Id: Ic37bec04707271168b68216217d60f4e8514e450