Substitutions can now be added

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Fix where big numbers with a lot of decimals would be displayed wrong

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Substitutions can now be edited

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Substitutions can now be deleted

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Substitutions are now actually substituted

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
ModelHelper now understands arctan

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Merge remote-tracking branch 'bas/basbranch2' into pull
Made ParenthesesHelper a lot more consistent (and less error prone)

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Keyboards should now be better fit smaller screens.
#99 should be fixed by this commit

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
removed the parentheses from the integral and fixed the d's of the derivative

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