RFR: JDK-8270195: Add missing links between methods of JavaFX properties

[Jonathan Gibbons]

Please review a medium-size update to the support for JavaFX properties in the Standard Doclet.

A JavaFX property is typically defined by a group of up to 4 elements:
* an optional field, which is typically private
* a no-args property method, whose name ends in `Property` and which returns an appropriate property object
* an optional getter method which can get the value of the property
* an optional setter method which can set the value of the property

Either the field (if present) or the property method (but not both) should have a comment describing the property. The rest should generally _not_have comments: comments will be automatically generated.

This change is primarily to improve the generation of the comments. `@see` links are generated between the methods for a property. In addition, improvements are made to the handling of `@return` ... adding it as needed, and removing it when not (the latter occurs when generating the docs for the property itself, using the info in the property method.)

There is some amount of cleanup to the implementation, most notably moving (and rewriting) the code to generate comments for property methods from `MemberSummaryBuilder` to `CommentUtils`,which is where most other synthesized comments are generated. However, the goal has also been to not unduly change the spirit and spec of the original code.

A new combo test for JavaFX properties is provided, that creates different instances of a class, containing different property-related methods with and without comments. Basic properties of the output are then verified for each property method: the description, any parameter info, any return info, and any links to other related methods.

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Commit messages:
 - JDK-8270195: Add missing links between methods of JavaFX properties

Changes: https://git.openjdk.java.net/jdk/pull/5102/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5102&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8270195
  Stats: 1024 lines in 12 files changed: 740 ins; 157 del; 127 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5102.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5102/head:pull/5102

PR: https://git.openjdk.java.net/jdk/pull/5102