Fixes based on more AtariAge forum feedback

• Fixed py2exe to include msvcp90.dll and friends
• Updated readme to include instructions on checking out modified Enthought libs
• Fixed page up/down in grids to be based on number of visible rows
• Changed max cursor position so can't position off the end of the document
• Fixed horizontal scrolling refresh problem in bitmap scroller
• Fixed file browser attepmting to open directories as files instead of expanding them