Support for showing all tests in curent workspace and picking which tests to run in vs code extension

[dakaa16]

A panel should be added to the Cobol Check view, where you can browse all tests currently in the workspace. The tests should be in a tree-structure like so:

• Source program
  • Testsuite
    • Testcase
      Each entry in the tree shows the status of the tests within - either pass or fail (shown with red and green icons). Source program and Testsuite can only have the 'pass' status if all tests within have passed. Each entry will have a 'run'-button when hovered over, which will run everything within. Each entry will be selectable, by clicking on it. If Source program or Testsuite is selected, everything within is selected as well. Every selected testcase should run when running the 'Run Cobol Check' command.