Add Full-Text search for various Java resources

[marchof]

An aggregates search should be added to quickly find various Java resources. An experimental deployment is available at https://javaalmanac.io/find/.

TODO

• [x] Index javaalmanac.io content
• [x] Add last package segment as keyword to index
• [x] Shorten method titles by showing local type names only in parameters
• [x] Count hits by tag
• [x] Add filtering
• [x] Add search box to javaalmanac.io page headers
• [x] Set focus on search field
• [x] button to load more results / infinite scrolling
• [ ] Index JavaDoc < Java 7
• [ ] Index language and vm specs < 7
• [ ] Index API diffs