Enable pinning when the ipfs daemon is in offline mode

Currently ipfs companion is completely disabled when ipfs is run in offline mode. I.e.

ipfs daemon --offline

However, it should still be possible to pin content when not connected to the network. That is

• This Page > Add to IPFS (Keep Filename)
• This Page > Add to IPFS
• Tools > Open Web UI

Should all be available. Also possibly

• Tools > Share files via IPFS

For this last menu option, the wording "Share" may introduce some confusion. On the other hand, presumably, someone that is savvy enough to run with --offline probably already understands that sharing will only take effect once they put the daemon into online mode.