phases: ``{phase}`` template keyword display the phase name ``{phaseidx}`` is providing the phase index as integer. This integer representation is useful when people need to use the fact that phase are ordered. Test keep using the number version for readability purpose.

phases: add a phasestr method on context

phases: add list of string to access phase name

phases: fix phase synchronization on push The bugs seemed to show up when element not in future common changeset should hold new hold phase data. The whole phase push machinery was rewritten in the process.