Add helper for selecting items from lists

[thisguycodes]

This warrants some discussion, particularly narrowing of scope. I wasn't given more information than this, but it's certainly a valid feature.

[thisguycodes]

There are two solutions here:

• Short term: add a custom ByClause to support this, it'll be xpath specific, which is why the long term option is planned.
• Long term: implement a custom element type (possibly subclassing the selenium element type), that supports our custom search methods being done on it