Fixed TOC anchor collisions in documentation-main.html

The table of contents' section links are generated from
anchors of class 'section. There were two collisions of
the anchor names, where two sections shared the same
anchor name:

Sections 'Test methods' and 'Test groups' both used the
	anchor name 'test-groups'
Sections 'Parallel suites' and 'Parallel tests, methods,
	and groups' used the anchor name 'parallel-tests'

Now, these are fixed, with anchor names that match the
section names, and the TOC links work properly.

The anchors for the table of contents are specified by the
name attribute.
Fixed section heading tags (<h3>, <h4>, <h5>) so they are consistent

Sections and subsection headers were inconsistent in their usage
of html heading tags.

The majority of section headings use the following tags based on
their indent attribute:

indent="." or blank =>  <h3>
indent=".."         =>  <h4>
indent="..."        =>  <h5>

However, some of the "..." level tags used <p><em></em></p> or even
<h3> some times. There were inconsistencies like this in a few places.

Now, all of the section headings conform to the above scheme.
Standardized section heading HTML format for easier reading/maintenance.

The HTML for the section headings varied between headings. Sometimes
the <h> tags were on surrounding lines, sometimes they wrapped the
content on a single line, and sometimes they were at the end of the
previous line of content. This made for difficult reading; it also made
changes difficult.

Now, all section heading <h> tags wrap the content on a single line,
in the following format:

<hx><a ...>content</a></hx>

so that they are easy to work with.

NOTE: I'm aware that this may not be compliant with some style guides,
and also that everybody has different preferences. I'm not trying to
enforce my particular preference over anyone else's; I picked this
format simply because A) section heading lines are generally short
enough to fit in screen-width even with <h> tags, and B) many of the
section headings were this way to begin with.
Updated version to be tested to 6.8.9-SNAPSHOT, in pom-test.xml.
testng-496 org.testng.junit.JUnit4TestRunner handles testAssumptionFailure as a failure but it should be ignored
Report test as skip.
Also report as skip from #testFailure with AssumptionViolatedException as failure exception
Remove unnecessary super calls. (RunListener is special not-implementation class)
Fix bug when test with assumption failure reported also as passed.
Add test for this case.