Contract test api

Limiting WASM exectuion time

- added account fetching in CLI
- added currency.abi file describing currency contract's ABI

- todo: some of the test are broken because the tests were malformed in
the first place (missing auths)

- refactored test/p2p/init/run_test.pl script to launch multiple producer / non producer nodes
use run_test.pl -? to see options.
- Fixed crash on exit. Turns out passing a shared pointer to a lambda-defined recv handler leaked a reference to a connection object. I had a debug log write in he connection dtor which fialed on program exit.
- Started implementing the efficient propagation of transations and blocks. More to do here.
- added hostname respolution to the http server config parser.

1. remove ordered_non_unique non-deterministic indices from producer
scheduling
2. added API to return contents of i64 tables
3. updated documentation to reflect deprecation of precondition and
validate
4. remove calls to WASM precondition and validate, but keep them for
native contracts