Add configuration option on where to store the target-shell history

[DissectBot]

For reasons we’d like to configure where to store the history file. By default, it should just be in the current users home directory (or the XDG data directory). But we also want the option to store it somewhere else. Current suggestion:

• In the .targetcfg.py you can have two configurable options
• First option is the base directory for a history file (e.g. /scratch/case/.history)
• Second option is the template filename for the history file (e.g. {uname}-{target_name}-history)

This all should provide the ability to have per-user, per-target and per-case history files.