Wrk Summarizer Parser

`wrk` is a utility for load testing a web-service over http/https.
`wrk` is similar in functionality to Apache's `ab` but differs in
that it uses event-notification systems and threads to create a more
realistic load from a single machine (thus eliminating/delaying the
need for master-slave configurations).

A parse was added to parse the output from `wrk` (generally sent to
STDOUT). This output is a summarized format and the parser generates
PerformanceReport(s) similar to how the existing JUnitSummarizerParser
does.

+ Added Summarizer Parser for `wrk`
+ Added test suite for new WrkSummarizerParser class
+ Added wrk output-files for testing (added to src/test/resources)
Updated .gitignore

+ added auto-generated test resources files (*.jtl.serialized)
Wrk Summarizer Parser Integration

+ Added DescriptorImpl extension to WrkSummarizerParser
+ Added DataBoundConstructor annotation to WrkSummarizerParser
+ Made cosntructor for WrkSummarizerParser public

+ Cleaned up HTML in report parser help file
+ Added default value for wrk to report parser help file
+ Added note to report parser help file about wrk output report

+ Added wrk to index.jelly's list of supported output formats/plugin
  description
Source Cleanup

Just some re-formatting to make everything consistent
Added Test for Wrk Parser

+ Added test for parsing wrk files that report error-stats
+ Added wrk test-file to test resources
Merge pull request #26 from JohnMurray/wrk-parser

Fixes JENKINS-21665