Feature/integrate kns client with 504 merge

[jgimeno]

This task cancels the PR for https://github.com/kowala-tech/kcoin/pull/637, it includes all changes done in the contracts by issue 504.

New Issues

• include tests for systemvars
• deregister oracle if the user deregisters the validator.
• stability contracts API.
• register validator must be called only from the mUSD contract.
• consensus mUSD token handler method - add method to say that mUSD is supported - check ERC223 spec.
• remove Domain() string method
• remove abi/bin

Closes #504 Closes #555 Closes #418 Closes #635

[yourheropaul]

I think the network IDs have got lost between the main net and the test net. They both have ID 1, but I think the testnet should be 2 in order to reduce network pollution.

It's replicable using the binary:

$ rm -rf ~/.kcoin && client/build/bin/kcoin --testnet init
...
INFO [08-28|09:53:43.233] Successfully wrote genesis state         database=chaindata                              hash=5a4d1a…e9c9b6

$ client/build/bin/kcoin
...
INFO [08-28|09:53:47.201] Initialised chain configuration          config="{ChainID: 2 Engine: konsensus}"
INFO [08-28|09:53:47.201] Initialising Kowala protocol             versions=[1] network=1
...
database=/home/paul/.kcoin/kusd/kcoin/chaindata

$ rm -rf ~/.kcoin client/build/bin/kcoin init
....
INFO [08-28|09:53:59.083] Successfully wrote genesis state         database=chaindata                              hash=18c73c…c453b8

$ client/build/bin/kcoin
...
INFO [08-28|09:54:01.576] Initialised chain configuration          config="{ChainID: 1 Engine: konsensus}"
INFO [08-28|09:54:01.576] Initialising Kowala protocol             versions=[1] network=1