Implement Windows-specific Timer class

This commit adds new Timer class written specifically under Windows
platform. Additionally, Timer is prepared for Linux implementation to ease
further development.

Timer tests are also added. These present basic usage and test some
specific cases.
[CRFIX]

This commit does following fixes coming from Code Review:
  * Boilerplates commented in one style
  * Added ImmediateStartStopTest
  * Fixed implementation of BasicUseTest according to discussed formula
  * Counter frequency is now acquired only once, during binary load
  * Division and casting is avoided in Timer::Stop()
  * Removed mStop from Timer class members
[CRFIX] Update #include directives
Merge pull request #41 from nfprojects/timer

Upgrade Timer class in nfCommon