MB-8386: Better system stats on Windows

This change replaces the aging Sigar library on Windows
with a WMI based implementation while keeping the port
functionality and interface identical. With WMI in place
now, future commits can tap into the extensive statistics
that the platform provides via WMI.

PS3 has important bugfixes, defaults missing values instead
of failing and adds a -debug switch for easy testing.

PS4 fixes total cpu to represent total elapsed cpu time
instead of total cpu time consumed to mimick sigar.

PS5 uses counters similar to resmon. It resolves the bug Alk
pointed out where >4GB was being truncated in 32-bit build.

PS7 uses Google's code style.

PS8 use our coding style.

Change-Id: Ia19e3b1d0954116c4de3b9f6ee1069fadbcadc55