Fix handling of properties for tuples and arrays of size 1

two issues were involved:

• the code of the corresponding Python Configurables was not correct (producing (1) instead of (1,))
• the parser was not able to understand something like (1,) (see #21 (closed))

I modified the parser to accept trailing commas in sequences (tuples, vectors and maps) and I modified Gaudi::Utils::toStream to add the trailing comma for size 1 tuples and arrays.

This may cause changes in the standard output.

Closes #21 (closed)