Move project documentation to docs.opendaylight.org

Let's keep the the project documentation closer to the code. Move existing documentation from OpenDaylight wiki to Maven generated site.

First explore capabilities provided by Maven and related plugins.
Choose language for documentation writing - analyze offered possibilities.
Create a raw outline for whole documentation including a short description for each section.
Discuss a proposal with community (users/developers).
Fill up the content (as much as possible), add various reports too.

The documentation update should became mandatory part of for new feature/enhancements tasks.