oops, fix regression in headless.lang
make Evaluator.runCompiledCommands/Reporter respect owner.kind

this is a bug or missing feature of long standing, only uncovered now
that I'm about to change headless.lang.Fixture to use these methods
minor code improvement in headless.lang
minor code improvement to headless.lang.Parser

also, sample-scala's tests.txt had an inconsistent test format, which
the improvement caught
code improvement in headless.lang.Fixture

DRY testCommandCompileError out of existence
put headless.lang.ParserTests in its own file
minor code improvement in headless.lang.ParserTests
in headless.lang, rename Procedure -> Declaration

since 'extensions' is allowed too
code improvement in headless.lang.Parser
shuffle code from lang.Parser to lang.Finder
beef up headless.lang.ParserTests
add package-level documentation for headless.lang