Split TimeFieldsProcessor

[rfc2822]

Splits TimeFieldProcessor into separate procssors for DTSTART, DTEND and DURATION.

• Added AndroidTimeField class to handle DTSTART + time zone in the same way as DTEND + time zone; also DTSTART + time zone is used at more than one location.
• The tzRegistry is now shared between all processors because it is expensive, and we want to use the same timezone objects for corresponding timezone IDs.
• We never generate DURATION in the iCalendar for compatibility reasons. This has been made explicit and tests have been added.
• AndroidTimeUtils class has been moved from ical4android to synctools package

[sunkup]

I assume the missing net.fortuna.ical4j.model.X imports are on purpose?

Looks good :)

[rfc2822]

I assume the missing net.fortuna.ical4j.model.X imports are on purpose?

Which ones do you mean?

Ah yes, there are two classes with name TimeZone, one from Java and one from ical4j. In the files where we need both of them we have to either use the full package name or use import … as, which I find more confusing.