create a version numbering

[Pierre Poulain]

PTools needs a version numbering (1.5, 2.0, ..) different from the bazzar revision numbering and more informative for users.

[Adrien Saladin (adrien-saladin)]

should we mark this bug as solved by the series/milestones system ?

[Pierre Poulain (pierrepo)]

> should we mark this bug as solved by the series/milestones system ?

Not yet since there is no reference to the milestone number in PTools files.
I advice we manually report the milestone number in the file version.cpp :
this->vernb = "1.1";