Don't output the entire csv.

We're not using it now and it just complicates the scripts.
Add --prefix option to prefix filename/columns.

This helps us split up output from multiple files that have the same
mib values.

Example: we have multiple netstat_$interface_1_second.txt files, they
ALL have columns that would cause the SAME files to be output such
as obytes.csv, by using a prefix we can make those files and columns
be named netstat_$interface.obytes.csv.
Use tranform.py --prefix to not overwrite data.

This avoids the problem where multiple EagleEye files had
the same name for columns.