update changelog for 1.2.3 release
update changelog for 1.2.3 release

paulmey/packer,pecigonzalo/packer,grubernaut/packer,rnaveiras/packer,tb3088/packer,ricardclau/packer,mkuzmin/packer,tb3088/packer,dave2/packer,tb3088/packer,tb3088/packer,pecigonzalo/packer,ricardclau/packer,dave2/packer,timsutton/packer,rnaveiras/packer,hashicorp/packer,timsutton/packer,KohlsTechnology/packer,rnaveiras/packer,paulmey/packer,KohlsTechnology/packer,youhong316/packer,KohlsTechnology/packer,ricardclau/packer,ricardclau/packer,mitchellh/packer,dave2/packer,hashicorp/packer,bryson/packer,tas50/packer,youhong316/packer,ChrisLundquist/packer,tas50/packer,tas50/packer,ricardclau/packer,KohlsTechnology/packer,hashicorp/packer,bryson/packer,mkuzmin/packer,KohlsTechnology/packer,rnaveiras/packer,youhong316/packer,ricardclau/packer,grubernaut/packer,paulmey/packer,ChrisLundquist/packer,dave2/packer,tas50/packer,tb3088/packer,ChrisLundquist/packer,dave2/packer,bryson/packer,mitchellh/packer,mkuzmin/packer,tas50/packer,timsutton/packer,dave2/packer,rnaveiras/packer,timsutton/packer,mitchellh/packer,bryson/packer,mkuzmin/packer,tb3088/packer,paulmey/packer,youhong316/packer,hashicorp/packer,mitchellh/packer,pecigonzalo/packer,ChrisLundquist/packer,mkuzmin/packer,KohlsTechnology/packer,timsutton/packer,ChrisLundquist/packer,bryson/packer,pecigonzalo/packer,grubernaut/packer,mkuzmin/packer,youhong316/packer,timsutton/packer,grubernaut/packer,ChrisLundquist/packer,paulmey/packer,mitchellh/packer,youhong316/packer,rnaveiras/packer,tas50/packer,bryson/packer,grubernaut/packer,paulmey/packer,grubernaut/packer