EPPT-2588: Fire Severity Index: Add a BuildUpIndex class to IMPROVER#2253

mo-philrelton wants to merge 5 commits intometoppv:EPPT_2411_fire_severity_index_workflow_developmentmetoppv/improver:EPPT_2411_fire_severity_index_workflow_developmentfrom

mo-philrelton:EPPT_2588_buildupindexmo-philrelton/improver:EPPT_2588_buildupindexCopy head branch name to clipboard