build net_api_plugin, link in net, net_api and txn_test_gen plugins, create something that calls the accepted_transaction signal

get_account API call should return info from totalband and voters tables in system contract, draft of pretty printing cleos get account #2661

 - added 3 new methods for chain::plugin_interface
    - sync incoming trx/block that should be used for legacy applications that need the exceptions/traces
    - a start_coordinator method
 - these new methods will only route to a single provider based on priority
 - migrated producer plugin to provide these 3 methods at a high priority
 - created validator plugin to provide these 3 methods at a low priority
 - validator plugin is default initialized, producer is no longer
 - validator plugin will start blocks and abort/restart as blocks come in

allow for block producer configurable leeway for cpu and net usage during execution (still checks against new limits without the leeway at the end of the transaction)

Using underscore makes it easier to double click and copy

- udpate system contract to set initial account bw to 0
- update system contract to process new on block header
- update cleos api and get info api

 - any transaction which results in an action trace being logged by the
 history plugin can be queried by get_transaction
 - support for short trx ids of at least first 8 characters (lower bound used)
 - return the trx receipt, block number, last irr block, and traces for
 actions that executed as a result of the transaction

* clean up configuration parameters
* use dynamic max_inline_action_size configuration parameter to limit size of inline actions
* use dynamic max_inline_action_depth to limit recursion depth of inline actions
* change deferred_trx_expiration_window parameter into a dynamic configuration parameter
* add numerator and denominator configuration parameters for later context free data discount implementation
* bill delayed transaction for the additional net usage of the eventual retirement of the deferred transaction

Last time I'll use the online github merger

start keos only if wallet host is localhost (check is simple and doesn't cover IPv6 or external IPs or hostnames of localhost) #2094