Improve block propagation

[karmacoma]

Belongs to: #449

• We should trust self-forged blocks and broadcast them before verification
• Every node should decide to include (or not) block on his own - so we should broadcast block immediately without verification (we can perform schema verification only)
• Decrease block size by removing empty/insignificant properties
• Use binary format, there are some libraries that we can use https://github.com/dcodeIO/PSON, https://github.com/mongodb/js-bson

[Isabello]

This Issue has been reopened for the following reasons:

It is insecure to forward a block that has not been validated. Deleting certain fields, while saving some bytes, is not secure, as it requires mutating the block multiple times.