Enable loading Excel files as data tables

[brynpickering]

What can be improved?

For some projects, it can be useful to store data tables in one Excel file. We'd just need the extra sheets option available in our data table definition. Of course, the standard caveats of working with Excel apply (namely, the datetime format automatically changing on save to match the device format).

Version

v0.7.0.dev5

[irm-codebase]

@brynpickering is it possible to add this feature without making our tables functionality super complex? In all honesty I think we'd gain more from supporting better defined formats (like parquet) than all the issues that come from trying to support excel...

[brynpickering]

We can add parquet to the list, there is even an issue for this to be added in v0.6 #694. In v0.7 it is possibly just a matter of updating the allowed suffixes with no change in the data table syntax. For excel it just requires a sheet_name option in the data table definition and fastexcel as an optional dependency, so I wouldn't say it will make it super complex.