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

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