Add ability to control inclusiveness of both sides of selection

[lindholc]

Calling select(..., inclusive=True) will make both the start and end inclusive. It would be good to control both sides independently.

Usually one wants the start to be inclusive and the end to be exclusive, which makes it easier to make multiple requests without overlap (time>=a&time<a+1 to time>=a+1&time<a+2 just works) or to get a whole period of time (time>=2020-01-01&time<2020-01-02 vs. time>=2020-01-01&time<=2020-01-01T23:59:59.9999....).