add row select to plugin table

[cshanahan1]

add row select method to Table and table mixin to allow selection by row index, indicies, or slice(s). Also adds 'select all' method.

[javerbukh]

LGTM!

[javerbukh]

Still good!

[gibsongreen]

Exposing these looks good to me! There were 2 things I was thinking about when testing.

One is if we want a more applicable Error to be thrown if there is yet to be a catalog loaded, or if the no sources were found and the user tries to select.

The second, I don't think deselecting a particular row would get much use from the API (although deselecting rows and deselecting all is possible from the UI), but deselect_all might be nice to have too.

[cshanahan1]

@gibsongreen thanks for the review, I added the 'deselect_all' method

I'm trying to decide what to do about warnings. Since this is not catalog plugin specific, adding a check in the table class's select_rows for the presence of a catalog doesn't make sense and I'm not sure if it would be worth doing this in the plugin by overriding select_rows, raising the warning, then calling table.select_rows. I think the resulting index error is fairly informative if you try to select from a non-populated table, personally. Happy to make this change though if you disagree

[pllim]

I'm trying to decide what to do about warnings.

If you want to keep it generic, maybe warnings.catch_warnings()?

[pllim]

For error, a generic try ... except ... would work but keep in mind that except gets expensive if hit too often. (And also make things harder to debug in the future.)