target-test-runner: exclude package and log4j jars

Fixes #12114.
MRC: fix handling of mode 16 data

Mode 16 denotes 8-bit RGB data, not 16-bit data.  See
https://trello.com/c/guQdSW8V/235-follow-ups-with-joaquin
Merge pull request #1091 from melissalinkert/mrc-pixel-type

MRC: fix handling of mode 16 data
Merge pull request #1080 from melissalinkert/test-runner-classpath

Exclude log4j and packages from target-test-runner