public class Sequencer
Return a sequence of Calls intermixed with in a sequence of non-Calls (
This class ease the rendering of the output with a jsp doing tag calls
For example "first Call(...) second Call(...) third"
The header is the prefix before a call. Note that if there era no more Calls,
the header is actually the footer.
The intended usage is
Sequencer seq = new Sequence(encoded);
Call call = seq.next();
output call print