Issue #530: Remove JXR library from launch.groovy

[nrmancuso]

Issue #530: Remove JXR library from launch.groovy
Ok, I wanted to provide as much proof as possible that this change has no ill effects; please let me know what else I can show.

First, a simple example using two repos that I created (note that my zsh prompt shows the branch that I am currently on, as well as my notes).
One has non-compilable code that should cause exception (broken-repo) and one has compilable code (not-broken) that should( and does) allow for a checkstyle-results.xml to be generated: https://gist.github.com/nmancus1/d097e9654130329200849742ccf0971c

If anyone would like to verify the above, here are the projects file lines:

#broken|git|https://github.com/nmancus1/broken-repo.git|master||
#not-broken|git|https://github.com/nmancus1/not-broken.git|master||

Note at the end of the gist above, I diff the two checkstyle-result.xml files, successfully.
This shows that launch.groovy works as intended after removal of JXR and associated code in launch.groovy.
The only difference in the end result of launch.groovy is that the final report is not correctly cross-linked, as shown in #527 (comment). This is not a problem, because we only use launch.groovy to create checkstyle-result.xml files and validate that checkstyle can parse specified repositories.

Next, diff.groovy uses launch.groovy to create checkstyle-result.xml files that it compares across branches. So, as proof that diff.groovy still functions as intended, I ran a diff report with config and projects file from checkstyle/checkstyle#9135, found here: https://nmancus1.github.io/remove-jxr-avoidescapes-diff/diff/index.html . It looks like we have lost the links to source files with violations. I am looking into this now, marked as draft.

[rnveach]

@romani I am good with these changes after my 2 comments, please review.

[nrmancuso]

Ok, links are fixed. Here is the output of a diff of the diff report found at checkstyle/checkstyle#9135 and the one produced by this branch of contribution with my changes: https://gist.github.com/nmancus1/122cb586904d6e2972e806acee5c07cd

The only differences are times, directory paths, and the lack of empty xref directories.