Allow max record numbers to be optional

[CarlosRuiz-globalqss]

At this moment the code enforces a max record numbers to be set.

I think it is good to have a default, but allows for a specific implementation to remove the max (my proposal would be setting the MSysConfig to zero).

And also for a specific query we could allow to skip the max record limit setting $top=0

[uthadehikaru]

when hit endpoint models/ without any param, the default value for $top is 0. i suggest to set $top=-1 to ignore max records size.