Documentation 2.0: living docs

Update of the original effort for choosing documentation platform [1].

Problem:

• Documentation is out of date because its painful to edit.
• Too many obstacles to contribute to documentation (difficult format, unclear where, need accounts, doesn't render immediately)

Additional/updated requirements:

• standardized on AsciiDocs
• readers/users are provided with a link to update the documentation on github, submit PR, merge
• automatically built and automatically deployed – live within 1-2 minutes

[1] https://developer.jboss.org/wiki/ChoosingDocumentationPlatformForModcluster