update to new mimeapps.list specification

[Vladimir Kudrya]

Please clarify this:
"add to the blacklist the names of any desktop files found in the same 
directory as the mimeapps.list file"
How "temporary" the blackist is in this algorithm?

If we are dealing with actions (add/remove), then why not to reduce 
complexity of the algoritm and just compose *one* list of associations 
from global to local by taking described actions?
1. go to the most global dir
2. Add from .desktop's
3. Add according to mimeapps.list
4. Remove according to mimeapps.list
5. move to next more local dir
6. goto 2

Strict linear logic, one list, no temporary lists, no 'if's, even no 
"implementation-defined behaviour", local always overrides, KISS.