RFR: 8277460: Add jwebserver tool

[Julia Boes]

This change introduces jwebserver, a dedicated JDK tool for the Simple Web Server. 

A description is provided in a follow-up comment.

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Commit messages:
 - update module summary
 - Merge branch 'master' into jwebserver
 - add version option, consolidate tests, update module and package level doc
 - drop "tool" in man page
 - Merge branch 'master' into jwebserver
 - update markdown
 - update troffl file
 - merge origin/jwebserver into jwebserver
 - initial commit
 - initial commit

Changes: https://git.openjdk.java.net/jdk/pull/6497/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6497&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277460
  Stats: 683 lines in 17 files changed: 603 ins; 22 del; 58 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6497.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6497/head:pull/6497

PR: https://git.openjdk.java.net/jdk/pull/6497