SERVER-7902 added support for global /etc/mongorc.js

The corresponding Windows path is
%SYSTEMROOT%\system32\drivers\etc\mongorc.js
SERVER-6400: do not use IN since its a macro on windows
Add support for checking if a mutable Element is numeric
Add function to check if a mutable element is an integral type
Rename SetModifier to ModifierSet
Refactor update SConscript