RFR: 8144062: Move jdk.Version to java.lang.Runtime.Version

[Iris Clark]

Hi.

Reviving this work from a few months back.

Please review the following changes to move jdk.Version to 
jdk.lang.Runtime.Version.

Bug

    8144062: Move jdk.Version to java.lang.Runtime.Version
    https://bugs.openjdk.java.net/browse/JDK-8144062

webrev

    http://cr.openjdk.java.net/~iris/verona/8144062/webrev.1/

When jdk.Version was initially pushed in jdk-9+1-5, it was
Improperly exported by java.base.  After exploring a few
options, the best choice was to move jdk.Version to 
java.lang.Runtime.Version (a nested class of Runtime).  By 
making Version an SE API, it may be exported by the java.base 
module.

As part of the move, a limited number of chnages were 
made to the Version class:

  - Change package name and class declaration (to static)
  - Eliminate use of "JDK" when describing a Java SE API
  - Initial clarifications related to zeros (trailing vs.
    Internal components)
  - Small typographical and grammatical enhancements
  - Indentation

The complete Runtime.Version specification is available here:

  http://cr.openjdk.java.net/~iris/verona/8144062/doc.1/java/lang/Runtime.Version.html

The old jdk.Version.current() was replaced with
Runtime.version().

In System.getProperties(), we indicate which version-related
system properties may be supported by Runtime.Version.

The remaining jdk and langtools file changes are all 
side-effects of changing jdk.Version.current() to
Runtime.version().

Thanks,
Iris