Feature/#36 non standard shifted keys

These are my first additions to allow defining keys for entering chars, that are normally only accessible by pressing AltGr(the right alt) and some key when the os keyboard layout is set to some european layouts.

Additionally I added some macros to enter otherwise dead keys directly. If I want to enter for example ~, I need to press AltGr and + twice.
Is this how dead keys are entered as non-dead in all (or at least most) non-US layouts? I ask because, if not, perhaps it would be better to separate out some of this key stuff, and make one file for US keys, another for German, etc. But that might be a bunch of unwarranted work. What do you think?