Fixes a fun little bug that's been screwing me over for awhile now.
Basically, tbuisp was checking if a file was an exe or srec based on extension. This was failing when tbuisp was invoked from xmlrpc, because the rpc server created a temp file without a .exe extension. Thus, tbuisp thought that the file was an srec (since it wasn't an exe)... and motes were not getting programmed properly. tbuisp now distinguishes which type the file is using avr-objdump, and matching the format. The downside of this is that we'll need to support different kinds of exe binary types as we add different kinds of motes (i.e., the binary type for our avr-based motes is elf32-avr... surely the telos motes will have a different type).