Refactor System.exit into return codes

[henrikglass]

See: cyrille-artho#27

In MBT.scala (line numbers):

• 216 @btellstrom
• 253 @btellstrom
• 272 @henrikglass
• 278 @henrikglass
• 292 @henrikglass
• 309 @henrikglass
• 455 @Pandington

In Modbat.scala

• 237 @Pandington

In Dotify.scala

• 209 @A1337li

Pick some.

[henrikglass]

I'm taking 216, 253 and 272.

[btellstrom]

I'll take 278 and 292

[A1337li]

I'll take 309

[ffsinger]

Taking 455 and 237

[henrikglass]

I added a "System.exit(1)" in Modbat.wrapRun. We need to change that to a return as well.

[ffsinger]

Lines 237 and 209 actually don't seem to need any change, the functions already return an exit code.