Added support for setting a sequence's current or next value as a default value.
Refactored SequenceFunction into SequenceNextValueFunction and SequenceCurrentValueFunction.
Both now extend DatabaseFunction.
Added method to database to generate the real value for a database function.
Added tests for the new functionality.
added some compile locations to gitignore
Merge branch 'sequenceComputed' of https://github.com/vorbis/liquibase into vorbis-sequenceComputed

Conflicts:
	liquibase-core/src/main/java/liquibase/change/ColumnConfig.java
	liquibase-core/src/main/java/liquibase/change/core/AddAutoIncrementChange.java
	liquibase-core/src/main/java/liquibase/database/core/H2Database.java
	liquibase-core/src/main/java/liquibase/database/core/HsqlDatabase.java
	liquibase-core/src/main/java/liquibase/database/core/OracleDatabase.java
Finish merge branch 'sequenceComputed' of https://github.com/vorbis/liquibase into vorbis-sequenceComputed