Forest plots cache plot and subplot requests

This reduces the number of requests dramatically when importing by plot
Row counting takes headers into account
Generate batches model
Generate batches scaffolding
Integrate batches into import process
Allows requests to specify a batch overwrite id
WIP batch uses Time instead of DAteTime
WIP batches know whether they were saved
Importers are provided with a batch id
Trees have a batch id
Trees update by batch overwrites
Merge branch 'batches'