store ...

Changed the behaviour of decoding rlp data. Something is considered to
be creating a contract if the 4th item is a list.

Changed constructors.

Contract and account now both have an address field or method for the
sake of simplicity.

Transactions can no longer serve as callers. Accounts are now the
initial callee of closures. Transactions now serve as transport to call
closures.

Status: Work in progress

Clients can set their own client string which will be send to connected
peers during the handshake.