NumberStyler: allow for space and underscore separation.

This allows people to enter numbers in a more visually kind way,
without breaking the general paradigm.
Calculator: expand number availability.

This adds the ability for numbers to contian spaces or underscores.  It
also makes me recognize once more how brittle all of these
inter-relationships are.
Merge pull request #752 from duckduckgo/mwm/styler

NumberStyler: allow for space and underscore separation.