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.

It is.

> you should not be affected by this anyway,

Well, given that I have to review each of those PRs I'm not unaffected.

> i've got plenty of more important things to do than fighting over such nits

So do I, but if we're going to quibble over style, I'll just say that I'll reject all your PRs in opm-core if the do not always carry braces on `if()`s from now on.