Replace bootstap implied tag closures with explicit tag closures

[zfi]

My Webstorm IDE is complaining about the HTML tag constructs used to manage modal windows. These tags are all closed with a '.../>' construct. The lint tool suggests that this construct is unsupported on some current browsers. It does not say which ones.

It goes on to suggest that the issue can be resolved by using explicit closing tags. Applying the recommendation is basically a no-op as far as changing the functionality of the HTML code.