Made some changes to the Packer templating docs
Made some changes to the Packer templating docs

1. Added the `user` function.
2. Some tidying up of language.

smaato/packer,routelastresort/packer,paulmey/packer,arizvisa/packer,youhong316/packer,dave2/packer,bryson/packer,dave2/packer,taliesins/packer,jen20/packer,timsutton/packer,tb3088/packer,ChrisLundquist/packer,jen20/packer,mkuzmin/packer,routelastresort/packer,paulmey/packer,ricardclau/packer,hashicorp/packer,jen20/packer,p1-nico/packer,ChrisLundquist/packer,paulmey/packer,jen20/packer,pieter-lazzaro/packer,c22/packer,sean-/packer,mkuzmin/packer,ricardclau/packer,grubernaut/packer,tsmolka/packer,pvandervelde/packer,arizvisa/packer,ricardclau/packer,pieter-lazzaro/packer,pecigonzalo/packer,tas50/packer,ricardclau/packer,mitchellh/packer,sean-/packer,timsutton/packer,pieter-lazzaro/packer,ChrisLundquist/packer,tas50/packer,tas50/packer,tsmolka/packer,c22/packer,KohlsTechnology/packer,KohlsTechnology/packer,tas50/packer,rnaveiras/packer,zhuzhih2017/packer,tas50/packer,youhong316/packer,taliesins/packer,rnaveiras/packer,tsmolka/packer,p1-nico/packer,jen20/packer,dave2/packer,markpeek/packer,pvandervelde/packer,p1-nico/packer,taliesins/packer,p1-nico/packer,c22/packer,ricardclau/packer,smaato/packer,KohlsTechnology/packer,pvandervelde/packer,boumenot/packer,dave2/packer,mkuzmin/packer,KohlsTechnology/packer,smaato/packer,youhong316/packer,arizvisa/packer,markpeek/packer,tb3088/packer,markpeek/packer,taliesins/packer,pvandervelde/packer,markpeek/packer,atlassian/packer,ricardclau/packer,mkuzmin/packer,c22/packer,routelastresort/packer,pvandervelde/packer,tsmolka/packer,ChrisLundquist/packer,youhong316/packer,paulmey/packer,atlassian/packer,p1-nico/packer,markpeek/packer,hashicorp/packer,KohlsTechnology/packer,pieter-lazzaro/packer,mitchellh/packer,routelastresort/packer,pieter-lazzaro/packer,p1-nico/packer,atlassian/packer,grubernaut/packer,youhong316/packer,youhong316/packer,rnaveiras/packer,bryson/packer,mkuzmin/packer,zhuzhih2017/packer,sean-/packer,bryson/packer,rnaveiras/packer,atlassian/packer,pvandervelde/packer,sean-/packer,smaato/packer,taliesins/packer,tsmolka/packer,paulmey/packer,pecigonzalo/packer,boumenot/packer,mitchellh/packer,KohlsTechnology/packer,sean-/packer,taliesins/packer,smaato/packer,grubernaut/packer,markpeek/packer,tb3088/packer,rnaveiras/packer,mkuzmin/packer,jen20/packer,pecigonzalo/packer,zhuzhih2017/packer,boumenot/packer,zhuzhih2017/packer,zhuzhih2017/packer,timsutton/packer,mitchellh/packer,ChrisLundquist/packer,tb3088/packer,boumenot/packer,smaato/packer,grubernaut/packer,c22/packer,boumenot/packer,paulmey/packer,arizvisa/packer,routelastresort/packer,bryson/packer,tas50/packer,atlassian/packer,tb3088/packer,tsmolka/packer,hashicorp/packer,arizvisa/packer,hashicorp/packer,timsutton/packer,mitchellh/packer,timsutton/packer,timsutton/packer,bryson/packer,arizvisa/packer,ChrisLundquist/packer,pieter-lazzaro/packer,grubernaut/packer,zhuzhih2017/packer,pecigonzalo/packer,dave2/packer,atlassian/packer,bryson/packer,tb3088/packer,c22/packer,dave2/packer,sean-/packer,grubernaut/packer,rnaveiras/packer