1318: Interval arithmetic support - First bits
- Make ValueError in Interval._new__ more verbose
- Implemented Interval.as_numer_denom via doctests
- Implemented Interval.as_base_exp without doctests (one liner)
- Implemented Interval.expand without doctests
  - If no deep expanding is requested, return self
  - If deep expanding is requested, do expand on Interval start and end.
- Implemented Interval.cancel without doctests
  - cancelling is done on Interval start and end
  - Eventually this implementation should be more sophisticated. PLEASE REVIEW!
- Implemented Interval.could_extract_minus_sign
  - Returns true, if start and end are negative
3972: Start of solve(floor (x)-5,x) should not raise NotImplementedError
First successful solve call solve(floor(b)-5,b,simplify=False,check=False) returned [(5, 6]] for b=Symbol('b',real=True)
First successful solve call solve(floor(b)-5,b,check=False) returned [(5, 6]] for b=Symbol('b',real=True)
Add support for element wise rounding of Set elements in RoundFunction
Merge branch '1318' into 3975