Specify sequence number with ff deploy

[celiacheff]

As a developer, I want to update easily my chaincode on my local instance of Firefly.
I can do the first deploy as intended, but obviousely later deploys must have a greater sequence number.
I understand that ff deploy is more intenteded for CI, but it would be a great feature for easier testing.

I have two suggestions:

1. add a --sequence/-s parameter or an additional optional arg to ff deploy to specify the sequence number
2. or automate the thing and make the sequence number auto-incremented (I've done this in bash by counting the commited chaincodes)

Thanks a lot