Impact Function Centric Wizard 

This PR contains:
- the wizard itself
- safe.utilities.analysis_handler.AnalysisHandler class for managing signals from Analysis and generating reports. The dock will probably reuse it in the future as agreed with Ismail.
- an additional signal in ExtentSelectorDialog to call it from the wizard
- changes to ImpactFunctionManager and ImpactFunctionMetadata, that were present in Ismail's branches the wizard is based on, but seems they are not merged to develop yet.
- a small fix to safe.test.utilities.clone_raster_layer

The "I would like to use a hazard/exposure/aggregation layer already loaded in QGIS" radiobuttons are selected by default if there is at least one compatible layer. Otherwise they are grayed out and the another radiobutton (a layer from browser) is selected.

This PR also satisfies #1078