Add a DataTranslator for NeuronConnect.xls data

[mwatts15]

Write a translator for NeuronConnect.xls and to the PyOpenWorm.data_trans package.

See other DataTranslator types in PyOpenWorm.data_trans.

The translator should read the XLS file, generate PyOpenWorm.connection.Connection objects, and produce a DataWithEvidenceDataSource.

derived from #25

[slarson]

@mwatts15 There is still desire from the community to use the original NeuronConnect.xls data set because of differing perspectives on the methodologies used to assemble them.

So I would say that data is not redundant.

Relatedly, it may be helpful to be able to select which dataset to use as a switch between multiple choices.

[mwatts15]

@slarson thank you for the attention to this issue. I tried to capture that the data may not be redundant in the issue summary.

[BioComSoftware]

@mwatts15 @slarson Can someone elaborate on the start position for this, and then functional end goals? I've found the PyOpenWorm repository, and see both files.