State saving and major rewrites

New:

• [UI] Save and restore calculator state across invocations
• [Converter] Save currency converter forex data after update
• [Calculus] Fix derivative accuracy bug which caused it to output zero every time

Translations:

• French (by Nathan Bonnemains)

Fixed:

• Code structure fixed and improved by Nathan Bonnemains
• [Calculus] Make Calculus button labels consistent with Scientific view

Improved:

• [Controls] Use Escape Key to close dialogues

Unit Converter Precision Override

Fixed:

• Override conversion precision based on unit for Currency and Data converter

Date Calculator Counting Fix

Fixed:
[Controls] Use F7 for last answer and F8 for changing angle mode
[HeaderBar] Change 'GRD' to 'GRA'
[Date View] Enable counting date backwards

Improved:
[Translations] Add more translatable strings

Initial Release

First release version of Pebbles