Config files for the nationalholiday plugin

Format is simple:
Standard-xml file. 
It must always enclosed by
<nationaldays>
...
</nationaldays>

then a short description tag.
<description value="german holidays"/>

for example. It should be used later on.

then a list of non-floating holidays follows, encapsulated with 
<entries>
...
</entries>

Each entry has the form 
<entry date="M-D" name="description of holiday"/>

floating holidays are not supported this moment.