Add a converter for python arrays

[hinerm]

Currently passing a python array results in it being wrapped in a single Java object. We should add a converter implementation to automatically unwrap python arrays to Java arrays.

Without a converter, python arrays have to be explicitly unwrapped, e.g.:

from jarray import array
blank=ops.createimg(array([100, 50], 'l'))

(thanks @bnorthan for that!)

[hinerm]

@ctrueden as far as I can tell the ConvertService is only invoked on the return value of a script... so wouldn't automatic conversion within a script require modifications to jython itself?

Per the JArray docs I think @bnorthan's solution may be the only one currently available.

Let me know if I'm missing anything..

[ctrueden]

@hinerm The OPS framework does convert input values as needed.

Regarding modules in general, you're right that inputs are not auto-converted, though see scijava/scijava-common#122 and scijava/scijava-common@290ce63.

[hinerm]

The OPS framework does convert input values as needed.

Sorry, right I forgot about inputs. But any statements in the script itself, such as local variable creation in this case, are never touched by converters.

[ctrueden]

See also imagej/imagej-ops#19, which will make things more complex once it is resolved: we will need to make sure that the OpService built-in methods have the proper type signatures.

[ctrueden]

But any statements in the script itself, such as local variable creation in this case, are never touched by converters.

I'm not sure I understand the concern. Can you give an example?

[hinerm]

@ctrueden and I talked briefly offline. We were talking about different things - we can't solve the general case (anonymous object creation in python) but we can solve the Ops case, because ops automatically converts it's inputs - which is awesome!

We also should add "goodies" converters like this for other languages' wrapped types.

[hinerm]

May be redundant after imagej/imagej-ops#115 which remedies the actual problem that started this issue.