Breakpoints - part 1

* setBreakpointByUrl
* removeBreakpoint
* setPauseOnExceptions
Implemented stack-trace/call-frames.

Frame scopeChain is not implemented yet.
Removed script name/url shortening.
Implemented resume & pause.
stepOver, stepInto, stepOut + setOverlayMessage

Implemented more debugger commands.
Removed session.js methods that are no longer used.