run foo for n does not set bitwidth

[edmcman]

I was very confused by the fact that this model did not find any instances:

sig Dummy {}

pred example { #Dummy = 8 }
run example for 10 //but 5 int

The problem is that run example for N does not increase the bitwidth, so N > 7 is useless without increasing the bitwidth. Perhaps a warning should be issued, or the bitwidth should automatically be increased?

[grayswandyr]

IMO, we should issue a warning for every command featuring integers that does not set the bitwidth explictly.

[grayswandyr]

Tracked in #30 .