Move numberOfDaughters() and daughter(size_t) outside class declaration

Break virtual inline. This will make `numberOfDaughters()` and
`daughter(size_t)` symbols with GLOBAL binding. Before it was in LOCAL
binding thus breaking compilation of `testCommonToolsUtil` from
`CommonTools/Utils`. Needed for GCC 4.9.0.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>