DE: provide additional characters on (unused) extended

[plata]

Currently, it is often required to switch to the special characters pages.

fixes #183

[KAMiKAZOW]

I'm not convinced by these changes. Why, for example, add the Euro sign to extended of D when it's already in extended of E like on regular keyboards? Same with some other characters. (I accidentally clicked on Approve before, sorry for the confusion.)

Misclick

[plata]

I've fixed the duplicate "€", that was indeed a mistake.

Yes, some characters are duplicate. The problem, however, is that there's basically no indication where to find them. For example, the dot key has '%' but the hint only shows '?'. So unless you know already where it is, you cannot really find it. Therefore, I've used the keys which had no "extended" assigned (like e.g. on Android keyboards).

Regarding duplication: There's already the umlaut key which is completely random in my opinion. It is duplicate of 'o' extended and breaks symmetry (why ö but not ü and ä?).