* ExpressionEdit improved in many ways:
	- History added
	- Highlighting for MathML added
	- Toggling between MathML-mode and Expression-mode enabled
	- Can tell if we are writing into a function (operator or ci) so we can help the user a bit (for the moment)
* GUI a bit remade, no more MathML or expression tab, everything goes into ExpressionEdit, can change with shift+TAB
* Variable edition dialog added. Useless but looks nice :)
* divide operators fixed (divide, quotient, rem, factorof)
* approx added
* Expression to MathML compiler optimized. Some operators treated as n-ary instead of binary
* Simplification option added (F2)
* Fixed PowerPC error, now should behave fine
* Function support added



