Implement right-padding of CHAR(N) datatype in PostgreSQL mode

When using CHAR(N) in PostgreSQL any inserted value smaller than N
characters will be right-padded with spaces to fill all N characters.
See: https://www.postgresql.org/docs/9.1/static/datatype-character.html

This change adds an additional Mode.padFixedStrings and set it to true
in the PostgreSQL Mode. Any value converted to a ValueStringFixed at
INSERT will be right-padded with spaces.

For additional infos see the H2 Google Groups post:
https://groups.google.com/forum/#!topic/h2-database/Luaxdrl137Y

Issue#479 Enhanced tests - removed comment about parameters not working for common table expressions - they appear to me to be working

Fix Travis Builds.

Issue#479 Allow non-recursive CTEs (WITH statements)