Low level improvments

some more scraps from the scatter shot PR. In addition to the patches requested, I added the one which changes the  	Well(Injection|Production)Properties code to the coding style of the module (and for the public API to the conventions also used by the rest of OPM).

This PR has some fallout in other modules, so merge sychronously...
It's also change for the sake of change. The original code was working perfectly fine and modifying this produces nothing but fallout build problems (cf., OPM/opm-core#677 and OPM/opm-autodiff#226).  Moreover, you're doing it wrong.  `ResV` to `resv` loses the fact that the original referred to the contraction of the words `Reservoir Volume`.