Merge pull request #2 from sebasguts/master

ToDo Lists
Merge pull request #3 from sebasguts/master

Fixed doc entries
updated .gitignore
Merge pull request #4 from sebasguts/master

Design fix
Merge pull request #5 from sebasguts/master

Some changes
Merge pull request #6 from sebasguts/master

Latest changes
Merge github.com:sebasguts/ToolsForHomalg into devel

* github.com:sebasguts/ToolsForHomalg:
  Added contrapositions.
  More documentation.
  Added trees and used them in ToDo-lists.
Rewrite of ToDo-lists.

TraceProof is not finished yet, also
some Display methods are not implemented yet.
Rewrote almost complete, some bugs left.
Added new functionality, changed syntax.

More Blueprints to come. Code needs some
cleanup. Tracking objects will become availible soon.
Rewirte complete, wait for proof tracking.