Updated doc with config

builder/digitalocean: fix response decoding after api changes

[skip ci]

website: address spelling mistakes

fixing version numbers: RCs should be labeled x.x.x-rcx

make it clear that "tools_upload_folder" is not used for esxi
[skip ci]

Fix typo in log statement

Support user variables for missing OpenStack string config options

Fixes #1506 

Boot command section in vmware and virtualbox ISO wasn't working
[skip ci]

builders/googlecompute: made formatting consistent

Also updated Debian 7 VM image to `debian-7-wheezy-v20150127`.

builders/googlecompute: fixed link in docs.

Clarify error message in case of an atlas client connection failure

When a packer json contains an atlas postprocessor, and `packer validate` runned locally
in case of the missing ATLAS_TOKEN env var, the following error message is displayed:

* Error initializing client: authentication failed

It wasn't clear which plugin produced this message, so the amazon-ebs builder was the suspect

Add Atlas post-processor documentation

see conversation with ryanuber: https://github.com/hashicorp/go-checkpoint/issues/2#issuecomment-73199209

Signed-off-by: gnawhleinad <danielleehwang@gmail.com>

Update Push APIs

This allows children to get the raw templates without re-reading the
file.

Fixes #1881 Don't include Windows Disks when packaging boxes for prl