Adds user-selectable hash merging support in vars

Port ec2 module to Boto

Update docsite/rst/who_uses_ansible.rst

Added Eucalyptus.

Fixes #1902.

Fixes #1908.

Update apt_repository to query if repo is already configured

Update examples/playbooks/ansible_pull.yml

Typo

This adds two dependencies to the apt_repository module:  apt and
apt_pkg.  These come from the package python-apt.  This is used to parse
the host's sources.list and examine whether the repo is already
configured.  This then eliminates the unnecessary
'add-apt-repository --remove' from running.

No need for deep copy (vars are essentially immutable once loaded, there
should not be any modifications)

Minor doc fix: service module 'state' parameter comments should be processed by RST

Hash variables are currently overriden if they are redefined. This
doesn't let the user refine hash entries or overriding selected keys,
which can, for some, be a desirable feature.
This patch let the user force hash merging by setting the
hash_behaviour value to "merge" (without the quotes) in ansible.cfg

However, by default, ansible behaves like it always did and if any value
besides "merge" is used ("replace" is suggested in the example ansible.cfg
file), it will also behave as always.

protect PluginLoader._extra_dirs from appending None

PluginLoader.add_directory() can receive None from, for example, 
Inventory.add_directory(self.basedir()) if host_list is a custom list.
None has no reasonable interpretation other than ignore it.

Add pacman to list of package managers in setup module

RabbitMQ Contrib

Update examples/ansible.cfg with sudo_exe

Make diagram of Directory Organization best practice match the text.

The text and playbook content assumed a directory structure that didn't
match the diagram.

- use boto instead of euca2ools
- improve error handling/propagation for run failures
- rename keypair to key_name (and preserve alias for old playbooks)
- should be 100% backward compatible with the euca2ools version

module needs to be passed to local_nvra

Adding it to runner's module_path makes it override local modules.

added info of required packages to build rpms

Adding default on vars_prompt

add when_changed when_failed example to docsite

--private-key tilde handling