Add __repr__ or __str__ to ReductionScript for easier reading

[Pasarus]

Currently the representation of the object is:

In [1]: from autoreduce_qp.queue_processor.reduction.service import ReductionScript
In [2]: rs = ReductionScript("INTER")
In [3]: rs
Out[3]: <autoreduce_qp.queue_processor.reduction.service.ReductionScript at 0x7faa68cd5a90>
In [4]: rs.script_path
Out[4]: PosixPath('/isis/NDXINTER/user/scripts/autoreduction/reduce.py')

It would be nicer if just doing rs prints out the script_path