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

nope, it's not. you should not be affected by this anyway, because I already fixed and opened PRs for all "consumer" modules at the same time as when I opened this PR, so why do you care?

> Moreover, you're doing it wrong. `ResV` to `resv`

honestly, i've got plenty of more important things to do than fighting over such nits. The opm-parser maintainer may decide and I'll obey!