All local storage paths in one directory and config argument.

Currently phantomjs stores offline application cache data and what it calls local storage data in a shared directory, while phantomjs has a command-line parameter for such data.  This patch places all of this data into the user-specified directory (--local-storage-path) so that it is possible to run multiple independent phantomjs sessions in separate processes in a single user session on a system.

This will affect any existing user of --local-storage-path who also uses offline application storage in their site.