Initial split of the modules and better documentation

[thomnico]

still WIP Using PR to collect discussion direction.

Remaining split will include fortios_cmdb_set

include only the set cmd.

fortios_cmdb_del and fortios_cmdb_get should be obvious.

fortios_config_backup fortios_config_restore.

fortios_license_check (this one could be reviewed as an Ansible fact if I understand that part correctly)

fortios_license_upload

fortios_monitor_get and post

That should be simple enough to avoid spending too much time on it and set the direction for the future developers.