Remove TO_DATE support from roadmap: It's already implemented

It's already implemented and working:
https://github.com/h2database/h2database/pull/150

Remove Java 6 backwards compatibility

Since we now require at least Java 6 we can remove the Java 6 backwards
compatibility layer.

Support byte[] in getObject

Add guards to JDBC debug code

The current implementation of getObject does not support byte[]. This
is an issue for some people [1].

 [1] https://groups.google.com/forum/#!topic/h2-database/InWprFw2B0o

Some of the existing JDBC code is missing guards around debug
statements that allocate strings.

Also build Java 8

To verify compatibility and for potential JSR-310 support
it would be good if we test against Java 8 as well.

fix compare TIMESTAMP WITH TIMEZONE

Added support to define last IDENTIFIER on a Trigger.

Tests for timestamps

since we no longer support jdk6

Implemented unit test.

Improve TimestampWithTimeZone javadoc

I found the comments in TimestampWithTimeZone not helpful in
understanding the semantics of the public methods.

This commit includes the following changes

 - add comments to previously not commented public methods in
   TimestampWithTimeZone that describe the semantics
 - add more verifications to TestTimeStampWithTimeZone to make sure the
   actual behavior matches the documented behavior

Change getters in TimestampWithTimeZone to int

The convenience accessors getYear getMonth and getDay in
TimestampWithTimeZone return long even though their values fall within
the range of int. This makes them a bit inconvenient to work with as
most APIs (Calendar, LocalDateTime) take int for such values.

This commit contains the following changes

 - change TimestampWithTimeZone#getYear() to return an int instead of
   a long
 - change TimestampWithTimeZone#getMonth() to return an int instead of
   a long
 - change TimestampWithTimeZone#getDay() to return an int instead of
   a long

Added missing source encoding. Assuming UTF-8.