Make ! actually optional when reading meta commands

[wwared]

Right now, Lurk treats (.lurk.meta.def a 123) and !(.lurk.meta.def a 123) (or !(def a 123), equivalently) differently, and only the latter variant with the explicit ! is understood as a meta command.

Both cases should instead be treated the same way, working as a meta command.

This does mean that (open ...) could be technically ambiguous if both .lurk.builtin and .lurk.meta are imported. The .lurk.builtin.open symbol should shadow the .lurk.meta.open symbol, so open is read as .lurk.builtin.open, and !(open ...) should be a reader shortcut for explicitly naming (.lurk.meta.open ...). This ensures we maintain the current behavior.

Whether this is done by having .lurk-user import .lurk.meta and then .lurk.builtin and having the latter import shadow the first, or by continuing to not import .lurk.meta and requiring the ! syntax on the REPL to name the meta symbols should not matter too much right now. The former is the intended behavior however, and should be preferred unless it causes issues.

Also need to double check that this does not cause issues with any demos or existing meta commands.