Support Anonymous Apex

[pwrightcertinia]

closes #65

Mostly a stripped down copy of the trigger member implementation for anonymousUnit. Does not impose any of the anonymous restrictions like disallowing static. Simply allows you to parse things like classes, methods and statements in the same file/block of text as you would find in a .apex script file.

Previously the check system tests only read sfdx-project directories, which avoided various invalid .cls template files that contain tokens like %variable%. Unfortunately this also means it won't pick up any .apex script files since they are outside projects. So it now runs an additional check using a list of certain samples that are known to have script files.

Manual test running check on samples had many broken .cls files, but no errors on .apex files:

Parsed 6246 '.cls' files in: /apex-samples
Parsed 227 '.trigger' files in: /apex-samples
Parsed 41 '.apex' files in: /apex-samples