OS Architecture check and installation path change

In certain circumstances chocolatey will install x86 version of zabbix
agent on 64-bit OS. For example running installation from 32-bit cmd or
using chocolatey like package provider for puppet who will execute
install from 32-bit cmd. In this case you get 32-bit agent running in
64-bit environment and unable to monitor 64-bit perfomance counters. Also
there is no need for "C:\Program Files (x86)" install folder as we have
separate version for each architecure.
Merge pull request #3 from applewiskey/OS-Arch-check

OS Architecture check and installation path change