Reference servers have to be installed in root directory [8.1]

During the migration to Blue Host the /yacs prefix has been removed, since we have installed the new instance of the software at the top-most level of the web directory.

One consequence of this, as pointed out by Agnès, is that all the staging script (used for software updates) has been updated to query reference servers correctly.

A side effect of this is that all reference servers will have to be installed at the root directory, exactly like www.yetanothercommunitysystem.com.