Test EVM EE with basic test case

[s1na]

I set out to create a basic test case to run the evm EE and have it pass. To get there I had to fix a few other things to. Therefore this PR is a combination of a few changes:

• It adds a new relayer that generates scout config files for a test case similar to the add11 state test. With the difference that instead of SSTORE it checks the expected value (sent to EE as part of block data) against value returned by evm code. Additionally the postStateRoot only takes value transfers into account, and no other state change (including metering).
• To achieve that it adds initial logic for MSTORE8 and RETURN opcodes. They only consider the last byte of offset though, this needs to be fixed.
• Modifies encodeAccount to accept account's state root and code hash, instead of encoding the default values.
• It also re-adds npm run evm to CI
• It makes the EE inputs codeHashes, bytecode and returnValue mandatory, since we now have the token logic in a different file and don't need to maintain backwards-compatibility.

Fixes #34

[lgtm-com]

This pull request introduces 1 alert and fixes 1 when merging aeda90b into a3c8cb2 - view on LGTM.com

new alerts:

• 1 for Useless assignment to local variable

fixed alerts:

• 1 for Unused variable, import, function or class

[lgtm-com]

This pull request fixes 1 alert when merging 6ad200f into 585a957 - view on LGTM.com

fixed alerts:

• 1 for Unused variable, import, function or class