libhive,libdocker: Allow more args to docker image building

[marioevz]

Adds more optional arguments to the client image building process.

Each argument can be appended by adding an underscore, a single letter, and a colon, to the client name.

Supported arguments are:

f: docker file name (used to build the client image)
u: user name (owner of docker/git repository)
r: repository name
b: branch or tag name

E.g.

--client go-ethereum_f:git_u:mdehoog_b:eip-4844

Specifies building image using Dockerfile.git, using git repository github.com/mdehoog/go-ethereum@eip-4844.

Branch as single unnamed optional argument is still supported:

--client go-ethereum_master

[marioevz]

Superseded by #767