WizardImport: Implement preliminary version

This implements a first preliminary version of the wizard responsible for
importing data. For now only CSV is supported and the data is actually not
imported in the end, but only a preview is shown.
lib: Add mysql connector
gui: model: Add preliminary version of model for JDBC
gui: wizardimport: Add tooltips to column page
gui: wizardimport: Add tooltips to CSV page
gui: wizardimport: Add tooltips to preview page
gui: wizardimport: Implement rough design of JDBC page
gui: wizardimport: Implement rough version of table page
gui: wizardimport: Activate JDBC button in source page
gui: wizardimport: Implement correct page ordering and finishing of the wizard
gui: wizardimport: Add height hint to preview table on CSV page
gui: wizardimport: Implement first draft of XLS page
gui: wizardimport: Activate XLS button and add the appropriate page
gui: wizardimport: Fix password property
gui: wizardimport: jdbcPage: Set error message in case of faulty connection
gui: model: Change return value of JDBC connect
gui: importwizard: Pass reference of wizard to pages
lib: Add poi
gui: wizardimport: data: Rename csvContainsHeader to firstRowContainsHeader
gui: wizardimport: Refine XLS page