Fixed bug in posh-docker setup instructions
Fixed bug in posh-docker setup instructions

There were two problems that this fixes.

1. Before this change, posh-docker was being installed twice. Once for the system (via NuGet) and secondly in the user's PowerShell context. This was confusing. I understand the reason was probably to create the user's $PROFILE file if it didn't already exist. I've replaced that functionality with clearer code.

2. The instructions had incorrectly said to add "Install-Module posh-docker" to the $PROFILE. Instead, this needed to be "Import-Module posh-docker".

londoncalling/docker.github.io,joeuo/docker.github.io,bdwill/docker.github.io,bdwill/docker.github.io,shin-/docker.github.io,joeuo/docker.github.io,docker/docker.github.io,johnstep/docker.github.io,JimGalasyn/docker.github.io,anweiss/docker.github.io,shubheksha/docker.github.io,johnstep/docker.github.io,anweiss/docker.github.io,docker/docker.github.io,shin-/docker.github.io,JimGalasyn/docker.github.io,phiroict/docker,londoncalling/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,phiroict/docker,joeuo/docker.github.io,bdwill/docker.github.io,phiroict/docker,docker-zh/docker.github.io,docker-zh/docker.github.io,LuisBosquez/docker.github.io,docker/docker.github.io,shin-/docker.github.io,joaofnfernandes/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,LuisBosquez/docker.github.io,bdwill/docker.github.io,londoncalling/docker.github.io,JimGalasyn/docker.github.io,joaofnfernandes/docker.github.io,anweiss/docker.github.io,johnstep/docker.github.io,anweiss/docker.github.io,shin-/docker.github.io,joaofnfernandes/docker.github.io,JimGalasyn/docker.github.io,shubheksha/docker.github.io,JimGalasyn/docker.github.io,anweiss/docker.github.io,phiroict/docker,joaofnfernandes/docker.github.io,shubheksha/docker.github.io,londoncalling/docker.github.io,LuisBosquez/docker.github.io,docker/docker.github.io,shubheksha/docker.github.io,johnstep/docker.github.io,LuisBosquez/docker.github.io,londoncalling/docker.github.io,shin-/docker.github.io,shubheksha/docker.github.io,LuisBosquez/docker.github.io,johnstep/docker.github.io,joaofnfernandes/docker.github.io,joeuo/docker.github.io,joeuo/docker.github.io,docker-zh/docker.github.io,phiroict/docker,thaJeztah/docker.github.io,bdwill/docker.github.io,docker-zh/docker.github.io,docker-zh/docker.github.io