Validate argument keys and fix -se short form

[micheleh]

Summary

• parseArgs() now validates parameter keys against a known set and throws IllegalArgumentException for unknown keys (e.g., typo --reportFile instead of --reportFiles)
• Added -se (single dash) as a recognized boolean flag alongside --se and --systemErrors, matching what the help text documents
• Both -se and --se work for backwards compatibility

Context

Since the initial commit (c71ed1f, 2021-11-15), parseArgs() accepted any --key=value without checking if the key was known. A typo like --reportFile=foo.xml (missing 's') would be silently stored, then the user would get a confusing "Parameter --reportFiles or -rf is missing" error with no hint about the typo.

Additionally, the help text documented -se (single dash) as the short form for --systemErrors, but the code only recognized --se (double dash). A user typing -se per the help would get System.exit(1).

Verification

• Unknown parameters (--reportFile, --bogus) are rejected with IllegalArgumentException
• Valid long and short form parameters still accepted
• -se works as a bare boolean flag (like --se)
• --se still works for backwards compatibility
• Full test suite passes (42 tests, 0 failures)