Refactored and simplified toDex part

These are the last commits for the toDex part of Soot that I had in the "pipeline" for some time now.

Although 34 files were changed, the Pull Request contains mostly refactorings for readability and simplification. Included is also one attempt to fix a bug with the ranges of exception handlers (see FIXME in soot.toDex.DexPrinter.toCodeItem()...) and one feature addition (the opcodes not-int and not-long are now generated if possible).