Fixes #9263

updated with some notes

Fixes #9247

This is an exceedingly rough sketch of what attributes might look like - metaclass implementations NOT complete.

Also adds a new class to the test_var_precedence test to check for
this type of error in the future.

Fixes #9178

Add doc of @filename in intro_patterns.rst

Fix several it's/its errors in the documentation.

Add readlink filter doc

Add one line example for looking up through etcd

As requested at request pull #9213, I'm proposing updathing this doc. Do you have man pages where I can update this too ?

Thanks

I noticed that the @filename notation for the --limit argument was not
conveniently described.

This patch adds a simple example to the intro_patterns.rst file.

Update the GCE guide with a working configuration.

Update guide_gce.rst

Update developing_modules.rst

broken link in developing_modules.rst