Fix problem on Liquibase.forceReleaseLocks() for H2 DB

There was a NPE on AbstractJdbcDatabase trying to het columnSize of
LIQUIBASE and MD5SUM
Made ColumnMapRowMapper respect SELECT AS column labels
Added support for finding foreign keys on Hsql databases
Merge pull request #101 from stephlag/master

Fix problem on H2 when trying to use forceReleaseLocks
Merge pull request #104 from siebz0r/master

Added support for finding foreign keys on Hsql databases
Checksum Doc and Tests
Documenting and testing ColumnConfig
Documenting and testing ColumnConfig