(QENG-797) Enhance Beaker to look for x64 installers for Windows

- add ability to install 64 bit pe builds (available for pe 3.4)
- add is_x86_64? method to host, convenience method for determining arch
  of host
(QENG-1026) Add support for x64 PE windows to Beaker

- default to installing 64 bit builds on 64 bit windows
- support install_32 host option, true = install 32 bit no matter the
  arch, false/unset = install 64 bit on 64 bit, otherwise 32 bit
(QENG-1129) support win64 open source builds

- add ability to install 64 bit windows builds
- supported when puppet version is 3.7+ or pe is 3.4+, and install_32 is not set for
  host or globally
- correctly update path post pe/puppet installation
Merge pull request #436 from anodelman/win-fix

(QENG-797) Enhance Beaker to look for x64 installers for Windows