Fix implicit dependencies of contracts source files

Set INCLUDE_DIRECTORIES property for every WASM target. This allows the scanning of implicit dependencies of every contract source file to work properly (IMPLICIT_DEPENDS)

Instructions to perform a full build with the WASM toolchain

Add exchange target as dependency for slow_test

This commit will likely break the currency and/or exchange contracts.

Update README.md

Updated Dockerfile to address issue #69

Create special accounts

Use cmake custom target to generate wast files

another round of incremental improvements for the p2p node networks.

limit active connection establishment to the identified seed nodes, but send forwarded messages to all connected peers

net plugin and genesis-timestamp

not quite perfect yet.

also adding interpretation of a --genesis-timestamp command line option to override that provided in the genesis.json file.
format of the timestamp value is either the ISO format yyyy-mm-ddThh:mm:ss (UTC) or the word now for using the current time
as the timestamp.

Replace hardcoded strings (active/owner) with global constants in config.hpp
Change char* constants to specific types and use N() macro for initialization