Added the ability to specify a schema as a database config variable and thus the ability for MRBS to work with databases containing multiple schemas (only applicable to PostgreSQL).   See SF Support Requests #431.

git-svn-id: http://svn.code.sf.net/p/mrbs/code/mrbs/trunk@2799 25f7e783-145e-4f2d-a9f8-dd7182bfe9c7
Minor improvement on previous change.   Qualified table names are now formed for all databases other than MySQL, rather than just for PostgreSQL.   As most databases other than MySQL seem to support schemas this will mean that should support for other databases be added in the future the code is more likely to work.

git-svn-id: http://svn.code.sf.net/p/mrbs/code/mrbs/trunk@2800 25f7e783-145e-4f2d-a9f8-dd7182bfe9c7