Announce pinning / unpinning via orbit

[sponnet]

Emit your pinning activity via an orbit channel. The channel name will presumably be the contract address.
A monitoring web-dApp could tap in to this channel to witness that his IPFS hashes are actually being pinned.

• Add a flag to enable announcing of activity ( --announce ) in the executable
• implement the orbit_ module
• define a format to show pinning / unpinning requests in the channel
• define a random identifier for the node
• optionally sign these messages using a proxy-specific private key to prove authenticity.