v3.0.0 - Xperience by Kentico v28 support

What's Changed

• Support Xperience by Kentico v28+ and multi website channel solutions
• Rearchitect the Lucene integration to support more dynamic content modeling
• Admin UI configuration of indexes
• Indexing reusable and web page content
• Updated docs

Work in progress

• Dancing Goat example solution
• Complete docs (index querying)

• Update README.md by @ondrejhenek in #22
• Feature v28 by @bkapustik in #24

Full Changelog: v2.0.1...v3.0.0