Create database indexes upfront in setup_db before starting the app.

This way we avoid race-conditions due to indexes not being created yet caused
by lazy index creation in mongoengine.
Merge pull request #777 from StackStorm/mongoengine_lazy_index_creation_race_fix

Create database indexes up-front in setup_db function before starting the app
Document "action-chain" and "mistral-basic" runners under the
"Available runners" section.
Fix typo - this should say mistral-v1 and mistral-v2.
Merge pull request #779 from StackStorm/update_actions_docs

Document "action-chain" and "mistral-basic" runners in the "Available runners" section
Support yaml metadata for actions and rules

* Add: Yaml support for actions and rules meta. Both yaml and yml extensions
are supported.
* Add: yaml, yml and json meta for sample action in fixtures for testing.
Add: Support for defining actions in yaml
Fixed some broken cross references in the doc
Merge pull request #783 from ojacques/fix/doc_crossref

Fixed some broken cross references in the doc
Merge pull request #782 from StackStorm/STORM-653/yaml_support_for_actionchains

WIP: Add: Support for defining action chains in yaml
Introduce a MetaLoader class for handling meta

* Add: MetaLoader class that can load content from json or .yml/.yaml.
Switch all registrars to use MetaLoader
Fix: Update st2 installation docs for vagrant and docker
Merge pull request #785 from StackStorm/doc_fixes

Fix: Update st2 installation docs for vagrant and docker
Add Google Analytics script to docs template.

also minor fix in start.rst.
Merge pull request #786 from StackStorm/DZ/add-docsite-analytics

Add Google Analytics script to docs template.
Cosmetic changes to README.md
Merge pull request #787 from StackStorm/DZ/cosmetic-README

Cosmetic changes to README.md
Update README.md
Fix: Explicitly use json.load and yaml.safe_load parse methods