adding tests for DbSource->length,
fixes#4150,
adding tests for DbSource->buildIndex(),
adding tests for DbSource->buildColumn(),
adding test for requestAction using a plugin,
adding DboSource->introspectType fixes#4224, refs #4589,
git-svn-id: https://svn.cakephp.org/repo/branches/1.2.x.x@6923 3807eeeb-6ff5-0310-8944-8be069107fe0