Fix non-void function return value

Since last catch insert exception string to `ss`, it should returns.

Changes to system contract, more testing 

Amazon: installing/upgrading boost removed build directory

Use shared_ptr to guard lifetime of bnet_plugin_impl and io_context

Resolved issues #3540 and #3541

Fix crash in bnet message handling

Richardian contracts for eosio.system contract

Fix small possible memory leak for WAVM module instantiate failure

- prevent bnet from sending trx before accepting a block
- fix fuzz13 build error

- null ptr for block and trx could be read, now checked
- varint decoding could over-shift a 32bit value, now it doesn't
- added a wasm file that could take wavm a long time to instantiate for
future testing

workaround for lack of timespec keyword python versions earlier than 3.6

fixes to get smoke tests working again; improvements to --genesis-timestamp handling

Also changes with --genesis-timestamp in chain_plugin:
 * Can only be specified on chain initialization.
 * Utilized for chain initialization even if --genesis-json is not
passed in as well.
 * Adjusts timestamp to nearest block interval even if an explicit
timestamp is passed in rather than "now".

Contract and actor whitelist/blacklist

Docker README.md "build" typo

Fedora: when installing/upgrading boost removed build directory