Add Library.insert(data)

[jkomoros]

In a lot of flows now you first have to create a temp_bit=Bit(data=data) and then check its id to see if it's in the Library and if not call Library.insert_bit.

Given how common that is, we should probably have a method like Library.insert(data=data) that returns a Bit with that data, inserting it into the library if it doesn't yet exist or returning the Bit with that id if it does. Perhaps it should return a tuple of (bit, was_inserted=False) so you can detect if it was inserted or if it was already there.