Add ability to install rbenv independently

- Can now install rbenv separately. Can be used as a requirement in a
  state for installing rbenv plugins using the git or file states
Fix description of method and whitespace lost
Add event function to state runner for light event interaction via CLI
salt.cloud.lxc: Optimized salt client
Safebelts for lxc provisionning:

Cloud:
    - Allow to use alternate config prefixes
    - Filter default options

LXC module:
    - Filter default options in create
Report errors when preparation fails

Previously salt daemons could fail to start without giving any
reason, when (for example) chown failed during the startup.
This change doesn't fix anything, but at least reports the error
back to the user.
salt.states.archive: multiple improvments

- add a new keep paramater to optionnaly not delete the archive after extraction
- Fix the traceback in case of tar error by correctly returning a state return mapping
- Correctly handle extra tar options if any by adding defauts ones if only needed
- Pep8
- When silently extracting with tar, be sure that the no output stuff won't be
  handled as a failed extraction.
Add pip_exists_action argument to virtualenv state

If you have some editable packages in a managed virtualenv than
you should be able to set the default action of pip for existing
paths.
lxc: saltify -> bootstrap; lxc & seed: doc improvements
salt.modules.seed: typo
blockreplace: append_if_not_empty ensure \n before mark
Fix master._clear_old_jobs for ext_pillars with root parameter
Revert "Fix #11003 TypeError: can only concatenate list (not "ImmutableLazyProxy(list)") to list"

This reverts commit 50fe12a5f515e3bb37ea0df7222b5c8c61229b63.
`ImmutableList`'s should also support `__radd__`. Fixes #11003.
Merge pull request #11072 from viraptor/startup_errors

Report errors when preparation fails
Merge pull request #11071 from makinacorpus/lxc

Lxc
Merge pull request #11074 from makinacorpus/archive

salt.states.archive: multiple improvments
Merge pull request #11079 from jarus/virtualenv-exists-already-action

Add pip_exists_action argument to virtualenv state
Typo fix.
Merge pull request #11089 from cachedout/typo_doc_fix

Typo fix.