Make manifest_file work as either file.pp or a directory

Fixes #2467 Add missing default values for 'disk_cache' and 'disk_discard' in qemu builder docs

Add missing default values for 'disk_cache' and 'disk_discard' in qemu builder docs, sort qemu_binary before qemuargs so it matches ordering from 'packer fix'

Add PTY to Docker exec

Added notes to warn against manifest_dir and note that manifest_file can be overloaded with a directory

Don't add ephemeral block devices to the EBS mapping

Merge branch 'documentation/ansible_inventory_groups' of https://github.com/Cbeck527/packer into b-ansible-inventory-docs

Fix inconsistent spelling

Use --portcount on VirtualBox 5.x

Don't override packer build version with min_packer_version from template

Guard against uninitialized pointers in io.Copy in WinRM calls

Fix go version in docs

The current link 404's, but this fixes it.

Thanks to copyedt on Twitter: https://twitter.com/copyedt/status/620807196259958785