RFR: 8253354: A jshell command to open desktop browser with specific javadoc query

[Jan Lahoda]

Adding a new command "/doc <element>" to JShell. This command opens the javadoc URL for the given element. A new
setting, /set browser, is introduced to actually set the browser that should be used to open the URL. If none
specified, JShell tries to use Desktop.browse (which may fail on some platforms).

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Commit messages:
 - Cleanup.
 - Fixing tests.
 - Cleanup.
 - Cleanup.
 - Cleanup.
 - Cleanup whitespaces.
 - Cleanup, javadoc.
 - Cleanup.
 - Sketch of a new /doc command for JShell.

Changes: https://git.openjdk.java.net/jdk/pull/521/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=521&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253354
  Stats: 614 lines in 9 files changed: 526 ins; 10 del; 78 mod
  Patch: https://git.openjdk.java.net/jdk/pull/521.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/521/head:pull/521

PR: https://git.openjdk.java.net/jdk/pull/521