Replace HTML Implementation with Bootstrap

## Is your feature request related to a problem?
The current HTML output is very legacy and it shows in many aspects. We need to replace the current HTML with Bootstrap (or another framework like it) to allow the forums to be more consistent across web browsers and devices - as well as standardize usability and form patterns for end-users.

## Describe the solution you'd like
Implement Bootstrap 4 (or newer).

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

## Additional context
The amount of effort would be quite high, but the complexity and difficulty would be easy to intermediate.