Fixes #68
* Also some parentheses placement fixes

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Added the toString() to MathParentheses and MathOperationSubtract

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Fixed a bug where EvalHelper inverted the base and exponent of a root

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
The state is now saved for FragmentMainScreen when rotating the screen.
This fixes #30

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Created convenience methods fromXML() in MathFactory

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
The evaluation dialog now saves its state when switching between portrait and landscape mode
+ Also set a maximum width for the evaluation dialog on tablets

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Fixed a bug where an integral with empty from and to children couldn't be sent to Wolfram|Alpha

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
The FragmentKeyboard state is now saved when switching between landscape and portrait mode

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