[Ml-yokadi] ical branch merge

[Sébastien Renard]

Hello,

I use ical yokadi server since few weeks without any issue, so I've merged it 
into master branch.
It is still incomplete from a feature point of view. In particular, it is 
read-only for now. But you know, release early release often. Write access 
will arrive later.
It is disabled by default, you have to use "-i" switch when launching yokadid 
to activate it.

a+
-- 
Sébastien