make using command helpers in ./stk500v2.js stateless

[soldair]

because we are async you really cant manage global state properly.
its the same reason nodejs doesnt expose fseek.

we should discuss.

stk500 seems to have 3 states. sign_on, programming, programming with internal address pointer.
we already don't use the internal address pointer by running loadAddress between pages. So we are either programming or not but we should always be signed on