Add tab completion for files and folders

[garydgregory]

For example "cd /foo" completes to "cd /foobar".

[jdillon]

cd command now uses a directory-completer; available in latest snapshot

[garydgregory]

No go: This only works for folders in the CURRENT folder. If you type "cd FOO/" and then TAB you get nothing.

[jdillon]

okay, likely more windows problems :-(