Reorganized sdk and cli to be two different packages in the same
repository

Moved sdk to cli repo

Rewrote SDK to match JS SDK implementation

CircleCI fix

…el with interceptor in service_client instance

optional parameter

Added call allowance to payment channel strategy as an optional
parameter

Split .gitignore to have a top level one and separate ones for each
package

Same for LICENSE

Updated CLI README, added top-level README (sdk-specific is still in
progress)

…manifest

this monorepo is organized as a PEP 420 compliant namespace
(https://www.python.org/dev/peps/pep-0420/).

The sdk package has been restructured to conform to the PEP 420
namespace package specification and it's under the "snet" namespace.

The cli package is both a regular package and a namespace package.

setup.py for the monorepo itself installs the dependencies for all
packages in the repository.

Each package and the overarching monorepo also have "requirements.txt"
files for local installations and CI enviroments: by installing via
"requirements.txt", the dependencies listed in "setup.py" are only
pulled and installed from PyPI if a local version is not already
available. This allows to get dependencies within the monorepo to be
installed from the local filesystem.

The whole package is called "snet" and gives the name to the namespace.
The subpackages are "snet.sdk", "snet.snet_cli" and snet_cli (since the
CLI package is both within the namespace and a regular package).
Going forward, all of the code in the "snet_cli" package can be migrated
to the namespace package: both were kept momentarily for compatibility.

In this scenario, everything inside the "snet.sdk" package has
visibility on the contents of the "snet.snet_cli" package and
vice-versa.
Everything inside the "snet_cli" regular package has visibility on the
contents of the "snet.snet_cli" package due to the regular Python import
mechanics, but it has no visibility on the contents of the "snet.sdk"
package (and vice-versa).
So, the shared code between the SDK and the CLI goes under the
"snet.snet_cli" package which is at "packages/snet_cli/snet/snet_cli".

Code and assets deduplication:

thanks to the new structure, everything under "resources" has been moved
to the "snet.snet_cli" package and is now shared between the SDK and
CLI. Specifically, this includes the json artifacts from the compilation
and deployment of the smart contracts, the raw ".proto" files to
interact with the daemon and the compiled python client libraries.

Changes:

since the CLI is both a namespace package and a regular package, changes
to the code have been kept to a minimum.
The only change of note is that state service does not compile its own
".proto" files at runtime inside the user's home directory anymore but
they are imported from the "resources" directory under the
"snet.snet_cli" namespace package, where they are compiled during setup.

getting abi for OpenChannel event from the contract object using web3
function

passing instance of payment channel management strategy to service
client

… package, moved version identifier

…d package

Refactored SDK package to use shared code