Add Peter Provost's PowerShell plugin for Vim

See headers of any of the committed files.

vim/indent/ps1.vim

@@ -0,0 +1,18 @@
+" Vim indent file
+" Language: Windows PowerShell
+" Maintainer: Peter Provost <peter@provost.org>
+" Version: 1.0
+"
+" $LastChangedDate $
+" $Rev 	$
+
+" Only load this indent file when no other was loaded.
+if exists("b:did_indent")
+  finish
+endif
+let b:did_indent = 1
+
+" PS indenting is like indenting C
+setlocal cindent cinoptions& cinoptions+=+0
+
+let b:undo_indent = "setl cin<"