Out of memory error when converting large cs files into csvxml

[rolfkleef]

When translating a large result sheet from csv into csvxml format, the basex program sometimes runs out of memory.

A 2.5MB Excel sheet might blow up into a 90MB XML version. Removing this step from the process a separate idea which will require more rigurous testing.

Fixes for now:

1. Add guidance on memory requirements for the docker container to handle such a file.
2. Add guidance on exit codes to detect these anomalies when processing a file that is too large.