Improve UI performance for getting repository list

Currently, there are several UI screens that trigger a full list of the repositories:

• Main page: in order to list repositories for quick "Set Me Up".
• When opening the Tree Browser to list all repositories.

The list of repositories takes several seconds for the UI to load, and the more repositories you have the more it takes.
From 2000 repositories and more the performance and user experience starts to be impacted. This also seems to be related to DB performance, and the more the DB is busy the more time this takes.

This JIRA is to improve the performance of this.
Rather by using a new cache mechanism for the repository list, or optimizing how we get the repository list, this has to be improved to support the growth of Artifactory servers.