Migrate from openpyxl to pyexcel for imports/exports

[weibullguy]

Describe the chore that needs to be addressed.
Change from the openpyxl to the pyexcel library for import/export. The pyexcel library provides more file format options by default and has plugins for the *.ods format.

dobranch
priority: low
type: refactor

• This issue subsumes the following issues:

[weibullguy]

Will also eliminate the pandas "FutureWarning: As the xlwt package is no longer maintained, the xlwt engine will be removed in a future version of pandas. This is the only engine in pandas that supports writing in the xls format. Install openpyxl and write to an xlsx file instead. You can set the option io.excel.xls.writer to 'xlwt' to silence this warning. While this option is deprecated and will also raise a warning, it can be globally set and the warning suppressed."