Removed assumption on Gitblit plugin name

Now the Gerrit plugin name is on the MANIFEST.MF: we do not need anymore
then to name it as 'gitblit.jar'.

Change-Id: I18c3b964760638ffa251b0b34e8641b12de8296c

Author: lucamilanesio

README.md

@@ -42,7 +42,6 @@ Configuration
 -------------
 In order to use GitBlit as GitWeb replacement, please apply
 the following configuration to your Gerrit config.
-(assuming plugin was copied as gitblit.jar)
 
     [gitweb]
         type = custom