Refactor `System.exit` into return codes or exceptions about modbat HOT 8 CLOSED

Refactored some uses in the commits shown above. 8 instances left.

from modbat.

For cases with deeply nested method calls, exceptions would be a better way of propagating error codes (as that would not require inserting "return" statements everywhere).

from modbat.

I'll review the earlier changes w.r.t. that and convert return statements to exceptions if appropriate, and will then move on to the forked repo.

from modbat.

Something was not done so well (my mistake...); check issue #45.

from modbat.

Existing changes to change again (to use exceptions):
14c1fe8

• ConfigMgr.scala: main
• ConfigMgr.scala: parseArgs incl. return type
• Main.main: use of parseArgs

03899e8
Already modified.

24a882f

Remaining uses of System.exit

from modbat.

Return codes left: ConfigMgr.scala (both 0 and 1): replace "return 1" with exception, remove "return 0", and make "run" have no return parameters; Main.scala: replace "return 1" with exceptions.

from modbat.

System.exit: a couple left; try:
find . -name '*.scala' | xargs grep 'System.exit'

from modbat.

Remaining open points:

• Modbat.explore should not have return code
• Main.run should not have return code
• Main.main should not not use return code of run (perhaps pending in a current PR?)

from modbat.