pylint fixes (remove unused functions, invalid function usages, unused variables etc.). Enable account balance validation.

Also fixed special accounts initialization and special_accounts_tests.

Moved special_accounts_tests and wallet_tests into unittests.

Move helper script llvm-gcov.sh into tools directory. Enable restart scenarios test. Add integration tests to coverage builds. Updated the restart test producer count to 4 to continue block finalization even with 1 node down. Use labdas to refactor wait based getter methods. Explicitly track node lifecycle to improve validation checks.

This is needed so that boost test framework doesn't steal the SEGV handler from WAVM

Enable nodeos_run_remote_test, distributed-transactions-test & distributed-transactions-remote-test. Add multi-producer support to enabled tests. Remove dawn2 support.

- use fc::app_dir() for platform-independent standard config and data
dir support
- no longer rely on EOSIO_DIR environment variable #2007
- enable short hand for setting contracts/abi by listing contract folder
    ./cleos set contract eosio.token ../../contracts/eosio.token

- fix account history plugin so that it works during replay
- disbled nodeos tests which are broken due to this change in nodes api

- disable mongo test that doesn't work
- remove extra param from set_resource_limits

- disable tests for nodeos until mogo is fixed

- fix bootseq tests
- related to #1614 and #1752
- new dispatch_inline helper
- define producer_schedule_type
- implement eosio.token as a independent contract in new contract style