Better template naming and added experimental a3 template
typo
partial fix for #760
adding a key_attribute keyword to the exposure layer makes the postprocessor use it
if not set the postprocessor will use the hard coded 'type' attribute.

this is only implemented at post processor level. Impact functions still need to be updated
Merge branch 'master' of github.com:AIFDR/inasafe
added key_attribute to the predefined keywords
Merge branch 'master' of github.com:AIFDR/inasafe into native_qgis_impact