Extension list from "Administration: XWiki Pro" is loading very slow

[msmeria]

Whenever I go to Administration -> XWiki Pro I need to wait approximately 30 seconds for the extension list to be displayed.
This time is very long and users might think the page isn't loading at all after waiting for some time.

[mflorea]

First, there is a loading indicator so the user should have no problem understanding that the list is loading. Then, the Jetty+HSQLDB distribution has all XWiki Pro extensions available in the local repository so the page should be loaded very fast in this case. If you use another distribution then the Extension Manager needs to resolve all the extensions from the remote extension repository which can be faster or slower depending on its load.

[mflorea]

For the WAR / Debian distributions we could implement a progress bar (we know how many extensions are in the list and we resolve them one by one, but we would need a job) and we could also show an estimation of the remaining time left.