Revert backwards-compatibility break in VMX option casing

PR #2309 introduced case-sensitive options in VMX files. This is to support a case-sensitive option called `virtualSSD`. The change made all options case-sensitive, which causes problems with external VMX options provided in user templates. To prevent breakage, this change is being reverted.

- Fixes #2574
- Reverts #2542
- Reverts #2309

Artifice post-processor

[WIP] Update packer docs related to Atlas

Add interpolation for .BuildName in compress output filename

Fix govet issues

Added go vet and git rev-parse head to appveyor so we can see what we're actually building / testing

Fix 'ephemeral' misspelling.

Add missing option

Add 1/10th second delay between key events to VNC for QEMU

Use go vet instead of go tool vet, and actually run it with make

Rename .html.md files to .html.markdown

Fixes #2546.  Make files under website/source/docs/provisioners conform to
standards for rest of docs.

Update code.google.com/gosshold/ssh to point to golang.org/x/crypto/ssh, since this has been moved into core now