- Omnibus 3.2.2 compatible
- Remove blocking packages
- Put all conf in /opt/datadog-agent since extra_package_file is not
working
- Use postinstall script for configuration and some cleanup
- Remove all traces of dd-agent user in conf
- Remove useless sudo

- Adapt build to new directory packaging/osx,
instead of the old one packaging/datadog-agent/osx

- Build for non-root use of datadog-agent,
update of postinstall script to set all correct rights

Build a GUI app with py2app
More precisely (everything is under win32 for now):
- gui.py
- images
- status.html

- ship supervisor and gohai in the app
(ship supervisor commands & cleanup
Take previous config is an app is already installed)

- fix all install issues due to spaces in path
- log to file pre/postinstall scripts
- set rights to current user
- launch the app at the end of the install
- doesn't install if same version and already installed

Update to {pre|post}install scripts so that:
- agent and App are closed before install if running
- agent and App are started after install
- exit if user used to install is root (we don't want to run the agent
  as root)
- add an internal `/run` directory, b/c `/var/run/dd-agent` is deleted
  every now and then

[osx] link conf.d to ~/.datadog-agent/conf.d

And update README & installer high-res pictures
And add a `datadog-agent` command in the PATH:

If someone wants to play with the agent using the command line.
Also fix a bug where the status was not working in the App started after
install.

And link all conf files to ~/.datadog-agent
Also (for simplification reasons):
the app is totally destroyed (except configuration, ofc) during the preinstall
script, to avoid any error and be in the same state for upgrade install for
postinstall.
Why do this ? Avoid Mac-behavior dependencies for the upgrade, it doesn't
always behave as it should.

See DataDog/dd-agent#1361 for more details about the
agent.
Consequences for dd-agent-omnibus:
- software definition of `datadog-agent`:
  * ship `datadog-agent` command line tool in install_dir/bin
  * delete GUI-only packages after app creation
  * do not delete anymore install_dir/{agent,embedded}
  * create and fill install_dir/etc conf directory
- preinst script:
  * use new conf dir `/opt/datadog-agent/etc`
  * delete agent pyc files
- postinst script:
  * some more logs for easier debug (logs are only visible in
  /var/log/datadog/preinstall.log)
  * use new conf dir