user module: return public SSH key

Return public SSH key if the user module is called with generate_ssh_key=yes.
Since "user" doesn't overwrite files, this also allows querying of existing
public keys.

Used in playbooks together with the "register" keyword, the returned key can be
passed to the "authorized_key" module allowing easy setup of SSH public key
authentication between remote hosts.

Use psycopg2's string handling to escape password string

Errors in Riak documentation.

Added catch-all exception for riak stats collection.

Explain conditionals as applied to roles.  I could also explain with_items but the scope questions are complex
here, and it is better to include such loops inside the imported tasks.

Prevent premature variable substitution in tasks

Quick fix for first_available_file and role support

As documented in #2623, early variable substitution causes when_
tests to fail and possibly other side effects.

I can see the reason for this early substitution, likely introduced
in 1dfe60a6, to allow many playbook parameters to be templated.
This is a valid goal, but the recursive nature of the utils.template
function means that it goes too far.

At this point removing tasks from the list of parameters to be
substituted seems sufficient to make my tests pass. It may be the
case that other parameters should be excluded, but I suspect not.

Adding a test case. I would prefer to analyse not just the aggregate
statistics but also whether the results are as expected - I can't
see an easy way to do that with the available callbacks at present.

This is a fix on top of the 'airplane variable upgrade' commits that fixes legacy when_string so it evaluates correctly in the new eval construct.

Add support for shallow clones in the git module

make bin/ansible error output consistent for shell module as for the command module when no arguments are given

implement --start-at-task option to hop to a specific task before starti...

Adds a riak module

make bin/ansible error output consistent for shell module as for the command module when no arguments

Typo in docs

Fix Jinja2 filter plugins initialization

Add base64 encode and decode filters to templates