608 suspend modes

[Stan185]

Fixes microsoft#608

Note that this PR contains code for handling source breakpoints and exception breakpoints. But in fact, VS Code Java only properly handles source and instruction breakpoints. I've left the code in there, since it's not completely trivial and it should not affect the behavior if no suspend mode is sent when setting the exception breakpoints.

How to Test

Set a breakpoint in a Java Program
Start Debugging
You now should be able to chose the suspend mode (thread or VM) in the breakpoints view and when editing the breakpoint condition.
Make sure the breakpoint can suspend either all threads or only one thread depending on the mode
Put your breakpoint in a for loop and when the breakpoint is hit, switch to the other suspend mode
Resume the program (may need "resume all" from the context menu) and ensure the new suspend mode is honored the next time you hit the breakpoint.
Make sure exception breakpoints behave as usual. There should be no UI to set the mode and exceptions should only suspend the thread the occur on.