detection for allday events with no VALUE=DATE

this should fix github #95 partly
understand EXDATE with another TZINFO than DTSTART

this should fix github #95 partly
handling rec. events with unsupported exceptions

these events won't be inserted into the db at the moment, instead a
warning will be printed

see https://github.com/geier/khal/issues/97
log extra values in the configuration file
typo
told configspec and with that doc about [sqlite] in config file