Fix UI bugs + new features + JS refactoring

[alaabenfatma]

Targetted issues

• Improve user interface #3 (points: 4 + 5)
• Repo rescan #36
• Repo rescan #36
• Search-bar does not work #42 (closing the following PR: Implemented the search feature #43, as a consequence)

Fixes and new features

Re-scan a repo using the categories instead of RAW rules

It is now possible to re-scan the selected repo using the categories.

Re-scan a repo using the Force mode

A checkbox to decide whether to scan a repo using the Force mode or not has been added to the (re)scan window.

Search for repos using the search bar

The user can make use of the search bar on the main page to search for repos.

Filter discoveries based on their categories

It is now possible to filter categories based on their categories using the buttons on the top-left of the window.

(In this example, the user will only see the discoveries that are under the access token category; of course, clicking on it again will disable the filter)

Javascript & Redundant code

The javascript code has been optimized: got rid of redundant code & refactored multiple parts of it.
Both the repos and discoveries windows are making use of the same scan modal, that said, I did collect all the code chunks that manage it within a new scanForm.js file, in which are contained all the functions that are needed to exploit the scan widget.

Future work

We may consider using web-components in a future PR.