Reverted recent java 8 changes

 * Reverted recent java 8 changes except legacyjavafixer injection
 * Code was bad, introduced new bugs, not really future-proof etc

 * Still unsolved: what if 1.6 or older packs have mods which does
   not work with java 8?
Merge pull request #873 from jikuja/revert

Reverted recent java 8 changes