Add support for problem-matchers

[samkhal]

The user should be able to specify a problem-matcher so that when a build is executed, the output is integrated with VSCode's problem view, in the same way as can be done with user-defined tasks.

If I understand correctly, this should be as easy as adding a new configuration variable and passing its value to the problemMatchers parameter when creating the task.

[Yablon]

I come across with this problem too