variants on grinder task def annotations

grind.dart

// dartdoc for the description; one combined annotation

/// Compile stuff.
@Task(depends: const [init])
compile() {
  ...
}

// dartdoc for the description; separate task and depends annotations

/// Compile stuff.
@task()
@depends(const [init])
compile() {
  ...
}

// separate annotations; description is an optional part of the task annotation

@task('Compile stuff.')
@depends(init)
compile() {
  context.log("Compiling stuff...");
}

// one uber annotation
@Task(depends: const [init], description: 'Compile stuff.')
compile() {
  context.log("Compiling stuff...");
}

// using a list vs lots of optional arguments
@depends(init, foo, bar, baz)

- use a list or lots of optional positional args?
- title case or lower case for annotations?
- one annotation or multiple?
- description in dartdocs, or in the @task annotation as an optional positional arg (or a named arg)?