Add calculus tab

[benetechMatt]

Title: Functions Icon: Integral

Buttons:

• Integral

• derivative

• limit

• sin

• sin -1

• cos

• cos -1

• tan

• tan -1

• Log

• ln

• ln10

• matrix. Able to choose the size

• long division

functions not built into mathlive

[sinabahram]

Many of these need proper accessible names.