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...
> 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.

no change from the current situation, then ;)