add program machine code as parameter to ROM and top_level,

change output of example assembler scripts,
update testbenches for programs 1 2 3 to use overloadable parameter,
formatted program3_tb

firmware/example_program1.sh

@@ -1,2 +1,2 @@
 #!/bin/sh
-python assembler.py machine_code.txt program1.asm
+python assembler.py machine_code_1.txt program1.asm

firmware/example_program2.sh

@@ -1,2 +1,2 @@
 #!/bin/sh
-python assembler.py machine_code.txt program2.asm
+python assembler.py machine_code_2.txt program2.asm

firmware/example_program3.sh

@@ -1,2 +1,2 @@
 #!/bin/sh
-python assembler.py machine_code.txt program3.asm
+python assembler.py machine_code_3.txt program3.asm