Rename vtkMap::ShowArea() to vtkMap::SetVisibleBounds()
Add GetVisibleBounds() method, to complement SetVisibleBounds()
Merge branch 'master' into john/show-area

Resolved conflicts:
	vtkMap.cxx
Register vtkLayer instances as they are added to the map
Merge pull request #64 from OpenGeoscience/john/show-area

John/show area
vtkMap should register layers when they are added.
vtkFeatureLayer should register features it adds
vtkGeoJSONMapFeature should register PolyData, also delete InputString
vtkOsmLayer should delete cached tiles
Remove memory leaks from qtWeatherStations class
Fix *big* memory leak introduced during vtkOsmLayer refactor

Was adding same map tile twice
Occurred sometime before commit 6149e4c6 (26-Oct-2014)
Fix issues in multithreaded layer, exposed by memory leak fixes.
More memory leak fixes
Merge branch 'john/object-lifecycle-fixes' into databrowser