Create a no-side-effects promise

[joente]

ThingsDB currently has a wse() function to enforce a side-effect. The opposite could be very useful as well.

A use case as an example:

response = {};
// some code could now set some properties on response
response.x = 1;
response.y = 2;

// return response;
response;

The code above doesn't require a change, but one is created as ThingsDB doesn't know it did not create a change.

Maybe we can create a nse() function; The wse() function (and functions which really do require a change) must then win from the nse() function, but for basic actions this could be useful.

[joente]

With pull request #333 we implemented a new nse(..) function which solved this discussion.