TogglePane: parent component for ui switching
MetadataBrowser: toggle between search and nav

However, the search field is not functional for now.
MetadataBrowser: stubs for button actions
MetadataBrowser: import cleanup
ProjectListDialog: swap first and second line in list item
TwoLineListCell: hopefully nicer style
MetadataBrowser: use two line list cells
StatementTableItem: fix value display for non string types
Merge pull request #66 from stoewer/gndata-editor-56-metabrowse

Further improved metadata bowser