Support for PostgreSQL and SQL Server

[gerritsangel]

Many companies use MS SQL Server, so this should be supported. While adding support for it, PostgreSQL should also be supported, because it is vastly superior to MySQL.

This should be no big deal, as Spring Data JPA and Hibernate are database independent. The only thing to note is to split schema.sql to schema-{platform}.sql and create different profiles for each database (mysql, postgresql, sqlserver). We can then just include the mysql profile in the dev and prod profile and voilà.