Keep record of registered layers in our testing CANVAS.
Use a fresh (not fresh instance, but a clean one) for each test.
Merge pull request #1117 from akbargumbira/develop

Fix tortuous 3 failing tests
Used temp folder to do testing to keep inasafe_data clean.
Merge pull request #1118 from akbargumbira/realtime_tests

Used temp folder to do testing to keep inasafe_data clean.
Merge branch 'develop' of https://github.com/AIFDR/inasafe into flood_categorising