[Core]: allow HTMLElement as template; [BS4] TooltipService and PopoverService fixes #1

[trollkotze]

1. In the Riba documentation it says:

A component object must define a template function, which returns the template for the component (this can be an HTML string or the actual element). It must also define an initialize function, which returns the scope object to bind the view with (this will likely be a controller / viewmodel / presenter). (emphasis added)

But to use an actual HTML element as a return value was not possible before. So I added it.

2. TooltipService and PopoverService, ported over from Boostrap 5 Alpha, had some type and logic errors which I fixed. (Not yet sure if full functionality is there. But basic tooltip works).

[trollkotze]

Replaced by new PR https://github.com/ribajs/riba/pull/18