Output category in progress messages

[apjanke]

__run_test_suite__ looks like this:

>> __run_test_suite__

Integrated test scripts:

  liboctave/array/Array.cc-tst ................................ PASS     21/21
  liboctave/array/CMatrix.cc-tst .............................. PASS     11/11
  liboctave/array/CSparse.cc-tst .............................. PASS     10/10
  liboctave/array/Sparse.cc-tst ............................... PASS    107/107
  liboctave/array/dMatrix.cc-tst .............................. PASS     10/10
  liboctave/array/dSparse.cc-tst .............................. PASS     12/12

but __run_test_suite2__ jumps right in like this:

>> __run_test_suite2__
Logging to: /Users/janke/octave/testify/logs/test-suite/testsuite-angharad.local-macOS-20190419_213043
  <Octave/tests>/libinterp/corefcn/Cell.cc-tst ................ PASS      4/4
  <Octave/tests>/libinterp/corefcn/__contourc__.cc-tst ........ PASS      1/1
  <Octave/tests>/libinterp/corefcn/__dsearchn__.cc-tst ........ PASS      1/1
  <Octave/tests>/libinterp/corefcn/__ichol__.cc-tst ........... PASS      1/1

The other way is better. And we've already added tags to MultiBistRunner to support it.