Install jmespath lib by default in the Docker image.

Document extra-dependencies for Ansible that could be installed.

Resolves #138

doc/install.rst

@@ -40,7 +40,7 @@ Now you can proceed with the installation of softwares used by Yorc.
 
 .. parsed-literal::
 
-    sudo pip install ansible==\ |ansible_version| netaddr
+    sudo pip install ansible==\ |ansible_version|
     wget \https://releases.hashicorp.com/consul/\ |consul_version|\ /consul\_\ |consul_version|\ _linux_amd64.zip
     sudo unzip consul\_\ |consul_version|\ _linux_amd64.zip -d /usr/local/bin
     wget \https://releases.hashicorp.com/terraform/\ |terraform_version|\ /terraform\_\ |terraform_version|\ _linux_amd64.zip
@@ -63,6 +63,15 @@ softwares should also be installed.
   
   sudo pip install docker-py
 
+For a complete Ansible experience please install the following python libs:
+
+.. code-block:: bash
+
+  # To support json_query filter for jinja2
+  sudo pip install jmespath
+  # To works easily with CIDRs
+  sudo pip install netaddr
+
 To support Ansible SSH password authentication instead of common ssh keys, the sshpass helper program needs to be installed too.
 
 .. code-block:: bash

pkg/Dockerfile

@@ -12,7 +12,7 @@ ADD rootfs /
 RUN apk add --update make openssh-client python python-dev py-pip gcc musl-dev libffi-dev openssl-dev && \
     mkdir /tmp/docker && apk fetch -o /tmp/docker docker && \
     tar xzf /tmp/docker/*.apk -C / usr/bin/docker && \
-    pip install ansible==${ANSIBLE_VERSION} docker-py netaddr && \
+    pip install ansible==${ANSIBLE_VERSION} docker-py netaddr jmespath && \
     cd /tmp && \
     curl -O https://releases.hashicorp.com/terraform/${TERRAFORM_VERSION}/terraform_${TERRAFORM_VERSION}_linux_amd64.zip && \
     cd /usr/local/bin && \