Previously, the first argument had to be a map, and the rest of the
arguments where passed as a vector as the second argument.
Now [my-comp foo...] generally behaves as (my-comp foo...).
Since `this` is no longer passed to component functions, add
current-component function.
Also change signatures of React callbacks, to reflect that arbitrary
arguments can be passed.
Remove set-props and replace-props for the same reason.
Add argv accessor and set-args instead.
Introduce set-state, replace-state and state functions instead.
Since we already have our own atom, it doesn't make any sense
to duplicate functionality. Also, the implementation was necessarily
very messy, and fragile.
