Disable osmosifying of raw functions

[samogot]

There is a "feature" that any function passed as one of properties of
object parameters to any command is replaced with than command. It is
rather inconvenience than handy, because it makes imposible to use
contextCallbacks in set command using object syntax. If setting several
simple properties can be bypassed, by calling set command several times,
using contextCallbacks for nested properties is completely imposible.

It is uncertain what was the reason behind such behaviour. It's hard for
me imagine where sole than command may be usefull in set or any oter
command parameter context. It neither documented, nor covered by tests,
so the proposal is to remove this "feature". This may cause some
regressions in some existing code that relies on such behaviour (is such
code exists), but it will be rather easy to fix by calling then commad
explisitly.

This commit also fixes #203 as type: () => "some string" now works.

[rchipka]

I believe the reason is because casting functions as .then() commands allows us to keep track of several things, like cloning and ref count of the data object, passing in context (this), and preserving data sort index.

I believe it is necessary and the tests should indicate as much, so if they aren't breaking with your changes they probably should.

That being said, the contextCallback functions should still work regardless of being deeply-nested in an object or array, even though they're casted to .then() commands.

[samogot]

Sorry, I don't even remember what it was about :)