adds :NERDTreeClose command and sets the filetype for the tree buffer to
"nerdtree"

dont ignore files like foo.c !

not sure how those tabs got in there!

dont warn windows users about setting NERDTreeChDirMode as drives are
handled properly now

delete oPath.NewMinimal cos it sucks and there is no need for it. It
was causing a bug with oPath.Equals on account of it wasnt correctly
determining whether a path found with s:GetSelectedPath() was a dir or a
file.

previously the RenameCurrent() view function was removing trailing
slashes from the destination path before passing it to oPath, now oPath
handles the slashes

If running windows, extract and cache the drive letter

note: the main motivation behind this is to encapsulate differences in OSs