Change depth class and flood terms to hazard level

[timlinux]

Lets use a more generic concept rather

In our data model we can change every mention of flood to hazard

And also depth_class to hazard_class

[timlinux]

For after demo please

[NyakudyaA]

This has been implemented in the staging DB

@ann26 cc @lucernae We need to change in the code all the references to flood tables espcially in staging