Removed 2048-sample mode

None of our DRS4 boards support the 2048 sample mode,
which seems to work only if certain optional parts are
soldered in place. It is maybe broken anyway and
definitely unused.
Added switch for gprof profiling

gcc support for gprog can be enabled by setting
the CMake variable ENABLE_PROFILING to ON.
Changed release mode dependent compile flags

Added -Wall in Debug mode an -O3 in release mode.
Fixed warnings after -Wall got enabled

Includes "trivial" C++ish things like unused variables
or empty return values.

A bug was fixed for ROOT datastreams, when a loop counter
was actually uninitialized and caused empty ROOT output!!
Added recording frequency status display

During data acquisition, display the current recording
frequency calculated by a gliding exponential averager.

After recording is finished, display the frequency
averaged over the recording of all frames.

Useful for quickly measuring the efficiency of different
output formats. Of course, it is influenced by many things
but a good starting point.