Extending DateAndTime Module

Addition and subtraction operators were added to DateAndTime. In addition some assembly macros were added to the system module.
Minor modifications/revisions to DateTime module:
* Added to() member that returns normalized DateAndTime object.
* new() now returns value wihout normalizing it first.
* parseStamp() now converts without normalizing.
Returns different error code if retrievePic() unable to open file. Wait added after camera powered down in retrievePic().
getPicture() now returns error code, along with retrievePic(). FileStream no longer used for image file (uses FSFILE instead).
Increased sync counter to allow more time to connect.
Improved camera sucess rate by allowing more time for startup.
Addressing Scanf Bugs

scanf bugs fixed by using legacy libs. See http://www.microchip.com/forums/m703149-print.aspx
Minor formatting and spelling corrections.