Added trees and used them in ToDo-lists.

TraceProof now works with them, to provide very specific proofs.
More documentation.
Added contrapositions.
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.
New Version number.
New functionality complete.

Some documentation for the Blueprints missing.
There is also no good view method for trees,
to see the results of the proof tracking.
Real Blueprints.
Documentation
Bugfixes etc.
Method for comparison can be added

to ToDoListEntries.
.gitignore and package number
Merge pull request #1 from mohamed-barakat/master

.gitignore and package number
Fixed bug in ProcessToDoList

which caused the entry list to be corrupted.
More Bugfixes.
Moved the www home.
Corrected www path in makefile.