set CROSS_COMPILE default to none

the default operation when CROSS_COMPILE is not set is to assume
that a native compile is taking place and use the stock gnu utils.
add new makefile environment variable UPLOAD_UTILITY

this adds a new make file environment variable UPLOAD_UTILITY that
provides the name of the application to be used to upload a binary
executable to the target device.
change upload function from AVRDUDE to UPLOAD_UTILITY

the base makefile was geared towards using avrdude to upload to
an arduino board. the AVRDUDE environment variable has been
changed to support a more generic context of UPLOAD_UTILITY. the
value for UPLOAD_UTILITY can be overridden from the shell.
update return code for ssh session completion

after transfering a file and executing it, if a ctrl-c issue to
stop the application a return code of 130 will cause the makefile
to halt on error. an if statement checks the return and exits with
a return value of 0 if a 130 error was found.