New PR job text should include our policy on running checkstyle

The PR text should include the following:

Our style rules for submitting code are as follows:

• If you add a new file it MUST adhere to our checkstyle ruleset.
• If you change a file (in a non trivial way) you are allowed (MAY) to reformat the code to conform to our checkstyle ruleset. If you choose not to reformat it then you SHOULD, where possible, try to follow the same style that's already in use for that file.

Checkstyle is enabled via a boolean property "-Dcheckstyle" to the compilation.

Note that we need our own property because you cannot override a plugin property that is already set in the plugin configuration section (ie -Dcheckstyle.skip=false does not work). The fix for this issue should include our new -Dcheckstyle property .