New config option to set heap size used when creating reports from UI

[lfcnassif]

Currently the report creation from UI uses java default min/max heap size. In some environments with few memory (e.g. 8GB) users are not able to create reports from large cases because of OutOfMemoryErros resulted from limited heap sizes chosen by the JVM (e.g. 2GB).

We can set the min heap size to 4GB when creating report from UI, and also externalize an option in config files to allow changing the min/max heap sizes if needed.

[gfd2020]

Maybe we can put a slider on the interface, like below. Would the minimum be the JVM default and the maximum some reasonable and configurable value by default, for example, 50% of physical memory?