.gitignore updates

Fix docker-compose-dawn4.0.yaml

Disable build of sql_db_plugin

- The resync option has been renamed to `--delete-all-blocks` to indicate what it is actually doing.

Upgrade Boost Version in CMake FIND_PACKAGE

CentOS: Boost version 1.67

Merging master into eosio_build_centos

system contract cleanup: remove special handling for eosio

Merge branch 'system-remove-eosio-specialcases' of https://github.com/eosio/eos into system-remove-eosio-specialcases

Amazon: changed boost version from 1.66 to 1.67

Update boost on coverage pipeline [skip-ci]

Build fedora, boost version 1.67

chain ID is now handled at runtime and is the hash of the genesis state; also the genesis state is included at the start of blocks.log

Add configuration arguments [skip-ci]

This reverts commit 0eda814c.

chain_id_type should be its own type (without a public default constructor) rather than just a typedef of fc::sha256 #3415

Special exceptions had to be made to `fc::variant::as()const` and
chain_plugin and net_plugin to access the private default constructor.
This is an ugly hack but it works for now. Eventually I need to see if
there is a better solution.

Update boost to 1.67.0 in builder [skip-ci]

Remove snapshot submodule.