Add a command to list breakpoints enabling id access.
Implemented breakpoint handling similar to gdb using breakpoint
ids (no longer delete and re-set all breakpoints on a change).
Save the module that is reported back in the session so that
it can be re-used for the next start. Keep a per-debugger-session
cache of fileName->Module for adding breakpoints to accelerate
setting breakpoints in the same file.
Polish the breakpoint tooltip.
