Add Form Elements (Input)

[wendigolabs]

Enhance and enrich Input component in @trendkite/ui.

See Add Form Elements for commentary, specific ideas, and description of work begun by @mikemfleming on Forms as a whole.

[wendigolabs]

Breaking this down into a number of steps. The end result shouldn't be a breaking change for rover/Input, though definitely a major version bump. rover/Input is used in 8 places in the trendkite-front-end codebase, and the work seemingly should be boxed in as a full conversion of tk-fe code to use Rover, and not use the tk-ui component.

• Make sure we've got good coverage in tests for current rover/Input and its "parent" components like AsString;
• Implement unit tests in rover/Input for current tk-ui/Input functionality that doesn't already exist in rover/Input (which is a lot) that exercise its current functionality. Currently there are no tests for tk-ui/Input that I could find;
• Port over tk-ui/Input functionality, creating Rover tests and Storybook examples along the way. How this funcdtionality translates to the way Rover layers functionality on top of base Rover/Input, and figuring out intelligent ways to expand that layering, will be part of this. Probably this step will metastasize into others;
• Verify that the handful of instances were rover/Input is used in tk-fe still work;
• Convert tk-fe features to use rover/Input, optionally adding feature-based testing as seems appropriate;
• Evaluate additional functionality to the expanded rover/Input that might be nice to have;
• Do that stuff;
• Profit?? (but probably more steps).

Comments welcome.