Array: add capability to insert while keeping a specific order

Array: add capability to insert while keeping a specific order

Adds two new functions, Util.lowerBound and Util.insertSorted,
that take an array, a value and a comparator, and find the
first position at which the value can be inserted without
violating the order, in optimal time.

https://bugzilla.gnome.org/show_bug.cgi?id=666429