RFR: 8277459: Add jwebserver tool [v6]

[Julia Boes]

> This change introduces jwebserver, a dedicated JDK tool for the Simple Web Server. 
> 
> A description is provided in a follow-up comment.

Julia Boes has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 16 commits:

 - Merge branch 'master' into jwebserver
 - update comment about exit code
 - add toolGuide tag to SimpleFileServer class-level documentation
 - Merge branch 'master' into jwebserver
 - fix whitespace error, add missing code tag
 - address PR comments:
   * update module and package summary
   * add -version / --version option to usage
   * fix markdown formatting
 - update module summary
 - Merge branch 'master' into jwebserver
 - add version option, consolidate tests, update module and package level doc
 - drop "tool" in man page
 - ... and 6 more: https://git.openjdk.java.net/jdk/compare/825e633e...936c3d4a

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Changes: https://git.openjdk.java.net/jdk/pull/6497/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6497&range=05
  Stats: 682 lines in 17 files changed: 587 ins; 27 del; 68 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