Added the derivative function and sourceview

Signed-off-by: bvanr <henkibrij@hotmail.com>
Fixed Wolfram|Alpha bugs.

Did this by giving all operators an appropiate toString method with good
parenthesing. Strings returned by Symja were ambigious to Wolfram|Alpha
in some cases and by building our own query strings we lose this
ambuguity.
Add checks so that wolfram|alpha only queries when it can.
remove unneccecery toString method in MathObjectEmpty
merge MathVariable and MathConstant to MathSymbol
Merge branch 'master' of https://github.com/Divendo/math-dragon
Created a keyboard for the variables

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
MathSymbolEditor now supports variables

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Merge remote-tracking branch 'folkert/work' into work
Merge branch 'master' of https://github.com/Divendo/math-dragon
derivative function and sourceview renewed

Signed-off-by: bvanr <henkibrij@hotmail.com>
added getType function

Signed-off-by: bvanr <henkibrij@hotmail.com>
Merge remote-tracking branch 'folkert/work' into work
The code is now using EvalHelper instead of the eval() method.
+ Also added support for roots, parentheses and constants in EvalHelper

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Symbols and empty boxes no longer light up when changing them

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Added a button for the imaginary unit to the keyboard

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
MathSymbolEditor now uses unicode superscript

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Added buttons for quick access to the variables x, y, z and t

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Merge remote-tracking branch 'bas/master' into work
Added the derivative operation to the drawer

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>