Fix semantics of IPFS daemon identifier

[machawk1]

In #609 with the integration of the renamed ipfsapi python module, we were required to update using HOST and PORT for parameters to a multiaddress (i.e., beginning with /).

In #609 @ibnesayeed noted that HOST implies a hostname where sometimes an IP might be used instead. The distinction of host vs IP for this address is significant, as the multiaddress for each would be different (see Important changes from ipfs 0.4.x), e.g.,

• ipfshttpclient.connect("/dns//tcp//http") (for hostnames such as localhost)
• ipfshttpclient.connect("/ip4//tcp//http") (for IPv4 addresses)

If an IPFS daemon is remote (#349), this distinction is again important.

Let's modify this to be a single string of host/ip:port and interpret this string on usage, building the multiaddress in the manner that is applicable to the specified host/ip:port.