Formulas question type for Moodle

This release add some features:

• combined feedback for each part of a question

• answer numbering (with the same choices that the core multichoice question type) for parts with multichoice answer

• text filters (for instance LaTeX and multilang filters) are correctly applied to multichoice part's choices and multichoice part's correct response

• new sigfig function to return a number displayed with a given number of significant figures (syntax: sigfig(number, precision). Please note that the result is a string and not a number as it can have trailing zeroes)

• For parts with a multichoice answer the correct answer is correctly displayed if you choose to display it (previously the index of the correct response in the menu or choices was displayed)

• the style of drop down menus and multichoice parts was improved.