Nested Search of Objects in Data Tables

[Pezmc]

Fixes #35 by:

• Adding recursive search of objects by default e.g. { rows: [{ name: 'Device 1', project: { name: 'Project 1' ] matches both Device and Project
• Adding support to :search-fields for nested properties e.g. ['project.name'] for the above to match only the project name field

I intend to refactor the filtering and sorting logic out of the data-table into a service/helper in a follow-up if there's time. This would have two key advantages:

• Increase (and simplify) testability by decoupling it from data-tables and Vue
• Opens the possibility for supporting different approaches (.e.g server side)

This PR is likely easier to review commit by commit.

[joepavitt]

Will wait @knolleary review before merging in case I've missed anything