CentOS 8 Support

• Update all mappings to add it
• Update userdata to utilize dnf ssm agent installation
• Update CentOS 7/8 to use new official AMI account
• Remove product code check for CentOS7 since it's no longer coming from marketplace
• Update example to use tmux instead of bind and bind utils as the later has inconsistent naming across OS families and versions

AmazonEC2RoleForSSM Deprecation Update

Fix instances of the deprecated AmazonEC2RoleForSSM AWS managed policy AmazonEC2RoleForSSM

Examples Update

• Create a dedicated example for custom AMIs
• Simplify README example
• Address Terraform 0.12 issues with the examples

v0.12.10

Merge pull request #74 from rackspace-infrastructure-automation/jcc/m…

…pcsupeng-1360

Userdata CFN Bugfix

v0.0.27

Merge pull request #75 from rackspace-infrastructure-automation/jcc/m…

…pcsupeng-1360tf11

Userdata CFN Bugfix for terraform 0.11

v0.12.9

Merge pull request #73 from rackspace-infrastructure-automation/0.12-…

…az-output

v0.12 - Add AZ output

v0.0.26

Merge pull request #72 from rackspace-infrastructure-automation/v0.11…

…-az-output

v0.11 - Add AZ output

v0.12.8

Merge pull request #70 from rackspace-infrastructure-automation/v0.12…

…-root-encrypt

V0.12 root encrypt

v0.0.25

Merge pull request #71 from rackspace-infrastructure-automation/v0.11…

…-root-encrypt

V0.11 root encrypt

v0.12.7

Merge pull request #67 from rackspace-infrastructure-automation/provi…

…der_bug

terraform provider issue