RFR: JDK-8282559: Allow multiple search terms in javadoc search [v4]

[Hannes Wallnöfer]

> Please review the first of two PRs to enhance JavaDoc search. 
> 
> This one focuses on the existing search script, to which it adds the feature to search for multiple terms. It also improves the implementation of case-sensitive search as well as rating of matches and provides some general update and refactoring of the script.
> 
> The search section in the help page is updated to mention the multiple search term feature, and I repurposed the last example to show the new feature.
> 
> The new search function can be tested here (top-level API doc files only):
> http://cr.openjdk.java.net/~hannesw/8282559/api.00/

Hannes Wallnöfer has updated the pull request incrementally with one additional commit since the last revision:

  Add comma as suggested in review

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8185/files
  - new: https://git.openjdk.java.net/jdk/pull/8185/files/8f178686..7d702a77

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8185&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8185&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8185.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8185/head:pull/8185

PR: https://git.openjdk.java.net/jdk/pull/8185