Add macro files for new contexts.

This request adds several new macro files that implement some specialized contexts:

* `contextAlternateDecimal.pl`, for allowing commas rather than decimal points (can be used to set course-by-course preferences without requiring problems to be re-written).
* `contextAlternateIntervals.pl`, for allowing reversed brackets to be used for open intervals (can be used to set course-by-course preferences without requiring problems to be re-written).
* `contextInequalitySetBuilder.pl`, for specifying intervals using set-builder notation.
* `contextPartition.pl`, which implements partitions of integers as sums of integers.
* `contextPermutation.pl`, which implements cycles and permutations.
* `parserRoot`, for adding `root(n,x)` to any context to provide nth-roots.