Add watch_item_eval to allow flexible selection of watch items for logics

***PROPOSAL***

Hi!

__This should just serve as a PROPOSAL how to allow flexibel selection of watch_items for logics!__

example from my own logic.conf:
<pre>
[nachtbeleuchtung]
    filename = 'nachtbeleuchtung.py'
;    watch_item = *.Automatikschalter
    watch_item_eval = [item for item in sh.match_items('*.Automatikschalter') if 'nacht_helligkeitswert' in item.conf]
</pre>

Works like a charm - of course it is somewhat hard for novices...

see
http://www.diveintopython.net/power_of_introspection/filtering_lists.html