Cleanup unused classes

These commits remove classes that have no references, except for freenet.tools.*. 
None of these classes appear to be used by:
* fred/FProxy
* any official plugin
* Sone
* Winterface

I'd like to remove a couple more classes to prevent people using them thinking they are doing it right (```SortedIntSet``` for instance, which is still misused in ~~WoT~~ Library), but that cannot be done without plugin changes (we have a chicken and egg problem here).
All official plugins (from the staging repositories) still compile after applying these commits (except for WoT, which I could not test as it seems to depend on ```FCPCallFailedException``` which is nowhere to be found).

Also, cleanup some unused imports.