swift:// path enhancements

[larsbutler]

For ZeroCloud applications, paths to many things are specified in the following format:

swift://AUTH_e799933a1f1a402b84655f9cf8d11680/example/example1.tar

Currently, the shortcuts ~ and . exist to represent the AUTH_e799933a1f1a402b84655f9cf8d11680 portion of the URL. ~ and . basically symbolize the "home directory" of the user.

I propose the following changes:

• Change . to mean "the current container" (instead of the account/home directory)
  • This is useful for making boot/system.map files a bit more generic. If, for example, a zapp reads a configuration file from the same container, it would nice to just specify . instead of hard-coding the container name.
• Support these shortcuts when specifying a X-Container-Meta-Rest-Endpoint for a container (when constructing REST APIs)