Package-level declarations

Fixes durations with day offsets with the 'T' prefix. See also https://github.com/bitfireAT/ical4android/issues/77

Some servers modify UTC offsets in TZOFFSET(FROM,TO) like "+005730" to an invalid "+5730".

Applies some rules to increase compatibility of parsed (incoming) iCalendars:

This is a pre-processor for iCalendar lines that can detect and repair errors which cannot be repaired on a higher level (because parsing alone would cause syntax or other unrecoverable errors).