Refactoring/fix UI build

[dukeofharen]

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

When the UI was opened (so on http://httplaceholder/ph-ui) the HTML was altered so the root URL was written to it. This result was cached, which means when HttPlaceholder was opened on another machine on the same network, the "old" root URL would still be inserted in the HTML.

What is the new behavior?

• The UI index.html is not cached anymore.
• First, when building the UI, the result was just a single HTML file with all CSS and Javascript. I split it again in multiple files, as this is also much easier when manipulating the HTML from the API.

Does this introduce a breaking change?

• Yes
• No