This class implements the emacs style completion action. Completion action is
a stateful action, as the user may invoke it several times in a row in order
to scroll the possible completions.
TODO: Sort by editor type
TODO: Provide history option
since: 3.1 author: Genady Beryozkin, me@genady.org
Creates a new action.
Parameters: bundle - the resource bundle Parameters: prefix - a prefix to be prepended to the various resource keys(described in ResourceAction constructor), ornull if none Parameters: editor - the text editor