use devstudioReleaseVersion=11 and path segment = /11/ for the devstudio update & build folders

Alexey and Tim think that using https://devstudio.jboss.com/10.0/stable/updates/ for the update site that contains 10.0, 10.1, 10.2, 10.3 updates... is confusing.

So, for devstudio 11, we could use:

• /11/
• /11.x/
• /oxygen/ (because this is based on Eclipse Oxygen)
• /e47/ (because this is based on Eclipse 4.7)