Update gen_ipbus_addr_decode to return non-zero exit code if it detects node address errors

[tswilliams]

Fixes issue #36

Also, changes format of error messages endpoint nodes with non-aligned addresses from:

main ERROR: Non-aligned base address detected: csr 0x43 0x1
main ERROR: Non-aligned base address detected: xpoint 0x57 0x2

... to:

main ERROR: Node 'csr' at 0x43: Width, 0x1, produces address mask 0x2 that is not aligned with node's base address
main ERROR: Node 'xpoint' at 0x57: Width, 0x2, produces address mask 0x4 that is not aligned with node's base address