PIVOT-864: Adding a "pluggable" file system browser to Pivot based on
Apache Commons VFS (Virtual File System).

Basically this is a clone of the existing FileBrowser and FileBrowserSheet
components with the names changed and using the VFS2 FileObject instead
of File everywhere.  The skins are cloned and changed also.

Currently it has only been tested with local file system browsing and
it doesn't yet browse into local .zip archives (for instance).  There
are some other features I may add such as found in the Swing-based
VFSJFileChooser.

The Commons-VFS and supporting .jar files are only necessary to be
available on the classpath if the VFSBrowser or VFSBrowserSheet
classes are instantiated.

I have added the basic .jars (current as of 24-May-2013) to the
wtk/lib directory and added additional classpath references to this
directory to several of the Ant tasks so the compile and test tasks
will work out of the box.

Tested the "clean", "package", "doc" and "test" tasks to make sure
they are all clean.

There are a number of remaining basic tasks:
- Need to figure out "getFileRoots" replacement (doesn't exist
  right now in VFS API).
- Need a way to specify a different URI scheme to browse to remote
  systems (such as http:// or ftp://) (such as an input text field
  or an ancillary dialog)
- Similary we need to deal with authentication, when required, for
  remote systems.
- Enhance the browsing to be able to browse into archive files in
  addition to just directories.
- Address the TODO: items in the code.


git-svn-id: https://svn.apache.org/repos/asf/pivot/trunk@1486223 13f79535-47bb-0310-9956-ffa450edef68