Add test for sourcefile
Refactor handling of source files and breakpoints

Breakpoints and Source files are now handled by their own objects.

Previously, after every step in/over, it would re-ask for breakpoints for
each stack frame.  Now, the BreakpointManager caches them.

The Breakpoint Manager now handles breakpoint messages

The File Manger handles sourcefile messages.  It caches the table layout for
each file (2-columns for line number and code) as jQuery objects, but does
not include breakpoints or current active line.
Print out the error message in the alert when an error occurs