Experiment definition: removed empty class comment. If it's there to
supress a warning then perhaps a comment is required. comment quotes are
not comments.
Xmap: changed numberOfMcas to numberOfElements to keep consistent with
other xmap classes. This was very confusing especially when trying to
debug or initially learn the system.
Xmap: changed numberOfMcas to numberOfElements to keep consistent with
other xmap classes. This was very confusing especially when trying to
debug or initially learn the system.

Also extend DetectorBase rather than DeviceBase. This is to keep it
consistent with live mode where the object is accessable from local
station without the use of the blasted finder.
Merge branch 'master' of ssh://dascgitolite@dasc-git.diamond.ac.uk/gda/gda-core.git