Change Bash prompt to utilize environment variable ACCOUNT_NAME.

Dockerfile

@@ -20,11 +20,13 @@ RUN apt-get update && apt-get install -y azure-cli
 
 # Configure Bash
 RUN cat <<'EOF' >> /etc/bash.bashrc
+
+# Include Git prompt helpers if available
 if [ -f /usr/lib/git-core/git-sh-prompt ]; then
   source /usr/lib/git-core/git-sh-prompt
 
   # Then PS1 can include __git_ps1 which is optimized and shows branch + state:
-  PS1='\[\e[32m\]\u@\h\[\e[0m\]:\[\e[34m\]\w\[\e[0m\]\[\e[33m\]$(__git_ps1 " (%s)")\[\e[0m\]\$ '
+  PS1='\[\e[32m\]AzureCLI (\[\e[35m\]${ACCOUNT_NAME}\[\e[0m\])\n\[\e[0m\]\[\e[34m\]\w\[\e[0m\]\[\e[33m\]$(__git_ps1 " (%s)")\[\e[0m\]\$ '
 fi
 
 export PATH=$HOME/bin:$PATH