Need capture added to syntax

[rwxrob]

Even though we have <-- to create a container instead of <- for "insignificant" checks it is common to not want everything on the right side and be able to further specify what should be contained in the capture. Most PEG related grammars will use <> for that with optional spaces after it. We need to add this to a version 2.0 of PEGN that includes better approach to _SOME for rhetorical things and instead just uses an empty rule with nothing but a comment in it to trigger the creation of a function for it with the comment as the body so it can be implemented in code.