Generalize non-digit-grouping of four-digit numbers

Generalize non-digit-grouping of four-digit numbers

In some languages it's conventional not to insert a thousands
separator in numbers that are four digits long (1000-9999).
Rather than copy-paste the custom code to do this between 13 files,
introduce another option and have the base Language class handle it.

This also fixes an issue in several languages where this logic
previously would not work for negative or fractional numbers.

To implement this, a new option is added to MessagesXx.php files,
`$minimumGroupingDigits = 2;`, with the meaning as defined in
<http://unicode.org/reports/tr35/tr35-numbers.html>. It is a little
roundabout, but it could allow us to migrate the number formatting
(currently all custom code) to some generic library easily.

Bug: T177846
Change-Id: Iedd8de5648cf2de1c94044918626de2f96365d48