fix issues found when use it with pyqt4.4 and numpy 1.3

git-svn-id: svn+ssh://controls01/siciliarep/svn/trunk/tango_client/ctrflyrtech_fdl/trunk@12942 a18efa20-c439-0410-bf20-9b91ec695b4c
Introduce dependencies in Facade signals and apply it to CavVolt_kV -> CavVolt_mV -> CavVolt.
fix the PDisCav_KW formula.
Use the np.arctan2 to fix some of the 'IF' statement in the Formula variables.
Merge remote-tracking branch 'gitcomputing/master'