Token upgrade

[DenisCarriere]

Change Description

Token upgrades related to circulating & max supply implications.

Deployment Changes

• [x] deployment of eosio.token contract
• [x] deployment of eosio system contract

API Changes

• [x] new ACTION issuefixed
• [x] new ACTION setmaxsupply
• [x] new STATIC method get_max_supply
• [x] new STATIC method get_issuer

Economic Changes

• [x] https://github.com/eosnetworkfoundation/eos-system-contracts/issues/127

Documentation Additions

• https://github.com/eosnetworkfoundation/eos-system-contracts/issues/129
• https://github.com/eosnetworkfoundation/eos-system-contracts/issues/126
• https://github.com/eosnetworkfoundation/eos-system-contracts/issues/125
• https://github.com/eosnetworkfoundation/eos-system-contracts/issues/127 (depends on https://github.com/AntelopeIO/reference-contracts/pull/66)

[DenisCarriere]

Moved to https://github.com/AntelopeIO/reference-contracts/pull/79

Due to conflict with Leap 6 upgrade