Improve plugin system

Allow to manage plugin installation order
Change log level for plugin installed warning

It could be usual case that plugin can installed already existing plugin,
because all plugins installing its dependencies
Merge pull request #224 from golyshevd/plugins

Plugins
Create links to documentation articles in README
Init quick start
Create alpha of quick-start
Rename how-to to guides
Init guides index
Create guides article index
Create reference index
Rename documentation files
Reorder documentation index list
Add installation guide to README.md
Add link do deps guide
Fix article header in quick start