Expose math functions in formulas

[ebruchez]

If we add a namespace for the Saxon math functions, things work. But they should probably be available out of the box, or a similar set.

XPath 3.x has them standard in the math namespace.

+1 from evaluator

[ebruchez]

We were going to just document, and we can still do that for older versions, but we can also add basic support out of the box, even before the full migration to Saxon 10.

• expose in http://www.w3.org/2005/xpath-functions/math the following function: log, sin, cos, tan, asin, acos, atan, atan2, log, exp.
• in Form Builder, scope xmlns:math on the root element if it is not present
• on offline branch, only do this on JVM side
• document

[ebruchez]

Documented