Add support for clients in client-common

[sagikazarmark]

For example methods client

[Nyholm]

We got the current clients:

• BatchClient
• PluginClient (added with configuration)
• HttpMethodsClient
• FlexibleClient
• EmulatedHttpClient (by FlexibleClient)
• EmulatedHttpAsyncClient (by FlexibleClient)

Should we support BachClient as well?

[dbu]

it sounds useful to have the batch client. i think there are use cases to want to send whole batches of requests.

[Nyholm]

Okey. I'll try to manage a PR with that as well.

[Nyholm]

Ive submitted a PR for the BatchClient as well. PR #103 will close this ticket.