fixed io issues (added constructor actually derive tree...)
deleted useless variables and fixed constructors
fixed bugs in new IO class
updated main
added throws OperationException for derive method
Merge branch 'master' of https://github.com/DamJos/Algo-SSD

Conflicts:
	Mission2Algo/src/mathtree/AbstractMathNode.java
	Mission2Algo/src/mathtree/AddNode.java
	Mission2Algo/src/mathtree/ConstNode.java
Merge branch 'master' of https://github.com/DamJos/Algo-SSD

Conflicts:
	Mission2Algo/src/Main.java