Web API Implementation

## Is your feature request related to a problem?
We need to transition the module to a more modern architecture. One of the steps required for this is to begin separating front-end and back-end logic.

As much as possible, the back-end needs to be Web API-based so we can have the option for an actual API that other extensions can use and the possibility of this module being forward compatible as much as possible for future DNN versions and/or a transition to an MVC module pattern. Doing this will also ensure the maximum amount of forward compatibility.

## Describe the solution you'd like
See above.

For the first phase of this, there shouldn't be any SPA or other similar work done yet. This first step should only be to separate front-end and back-end logic and code as much as possible.

Later, we can then consider reorganizing views and/or implementing more SPA-based implementations.

## Describe alternatives you've considered
None at this time.