make it easier to run multiple cougarvision instances at once

[kgarwoodsdzwa]

currently, it's difficult to run two instances of cougarvision on the same computer in the same directory, because they both would access the "last_id.txt" file in order to retrieve the newest images from strikeforce. if this was a configurable parameter in config, where one points to which last_id file to use, then multiple instances could run at once. this is in an effort to test checking for bobcats before rolling it out to other users, while the cougar alert is able to keep running on cougarscent and sent to all consumers.