Add win_system state, refine win_ntp module

This pull request includes several changes/refinements:

1. The win_ntp module has been refined slightly, using built-in service support to restart the ntp service rather than chaining together ``net stop w32time && net start w32time``.
2. A bug in how ``service.status`` module identifies services in the process of stopping/starting was fixed, and ``service.restart`` was cleaned up and simplified.
3. A new function was added to the win_system module, that identifies computer hostname changes that are pending reboot.
4. A new state module was added to manage the system's hostname/description.
5. New states/modules, as well as some missing windows states, were added to the docs.