Allow Sub Folder Operation

Some people find that having a whole virtual server dedicated to a thing like a calendar can make it more difficult to install, or is undesirable (particularly in very small installations.

Currently RSCDS requires a full virtual server because all paths begin with "/", like:

http://calendar.mcmillan.net.nz/caldav.php/andrew/work/

This would be changed to allow something like:

http://andrew.mcmillan.net.nz/calendar/caldav.php/andrew/work/

Approach
The existing virtual host needs to:
 * allow following of symbolic links (i.e. "Options FollowSymLinks" in Apache config)
 * have a symlink to the 'htdocs' directory of RSCDS as the subdirectory (i.e. from inside the existing virtual host website).
 * have the AWL include path set.

Status
Completed and checked into Git for release 0.5.0.