RFR: JDK-8248863: Add search landing page to API documentation [v3]

[Hannes Wallnöfer]

> This is the second of two PRs to enhance JavaDoc search, it is based on the first one (#8185).
> 
> It adds a standalone search page (search.html) along with its own script file (search-page.js). This PR is very similar to the last prototype I uploaded and demoed, the changes are mostly tweaks to the markup, style sheets and text. 
> 
> JDK API docs rendered with this patch can be viewed and tested here (top-level files only):
> http://cr.openjdk.java.net/~hannesw/8248863/api.01/

Hannes Wallnöfer has updated the pull request incrementally with two additional commits since the last revision:

 - Use different max results values for popup and page search
 - Fix search link height

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8226/files
  - new: https://git.openjdk.java.net/jdk/pull/8226/files/b47c7346..27e057fb

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8226&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8226&range=01-02

  Stats: 5 lines in 2 files changed: 1 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8226.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8226/head:pull/8226

PR: https://git.openjdk.java.net/jdk/pull/8226