RFR: JDK-8239804 : Cleanup/simplify HTML/CSS for general block tags

[Jonathan Gibbons]

Please review a change to cleanup/simplify the HTML and CSS used to 
present block tags, like @see, @since, etc.

Currently, the information from these tags is presented in a definition 
list (<dl>). The labels, in the <dt> nodes, are wrapped in <span> using 
an inconsistent set of CSS class names. Sometimes the names are shared, 
sometimes they are unique.

With this change, a new CSS class "blockTags" is put on the enclosing 
<dl> node, and the <span> nodes wrapping the individual labels removed. 
This does mean that it is no longer possible to style some of the labels 
individually, but the use of CSS class names that were sometimes shared, 
sometime unique, makes it unlikely that anyone tried to do this. If (and 
only if) there is a demand to style tags individually, that should be 
handled as a new Enhancement request, that might involve putting 
tag-specific CSS class names on the <dt> and <dd> nodes for each tag 
(i.e. without an additional <span>).

There is one anomaly. The definition list for the block tags for a 
method is also used to present information when the method overrides or 
implements a method from a supertype. That makes the new CSS class name 
of "blockTags" slightly less than ideal. Suggestions for a better name 
are welcome.

The code to generate the overall list of tags for any element is not as 
centralized as might be desired. This changeset does not attempt to fix 
that.

There should be no visible change to docs generated using the default 
stylesheet when the docs are viewed in a browser.

The src/ code changes are relatively simple, and just consist of 
adjusting the HTML and CSS that is generated. In some cases, there is 
some additional code cleanup. About 30 tests are affected, although the 
changes are generally simple and localized. The bug number has been 
added to the @bug list for a subset of the tests; there are no new 
additional tests.

---

A separate exercise would be to identify other <dl> nodes generated by 
the doclet, and to add a CSS class to those nodes to identify the kind 
of list.

-- Jon

JBS: https://bugs.openjdk.java.net/browse/JDK-8239804
Webrev: http://cr.openjdk.java.net/~jjg/8239804/webrev.00/