A peer is allowed to change their ID during TS_COMMITTMENT

Typos and comments/docs/logs/README adjustments
Sending market.cancel moved into trade impl.
Fix of memleaks

Path to trade directories and their creation
Definition of generic trade operations
Definition of overriden trade operations for the trading type 'basic'
Declaration of trade parsing functions

New message type 'encrypted'
Encrypted payloads and their types
Order internal structure definition
Trade internal structure definition
Declaration of the first trading protocol 'basic'

Encrypt/decrypt message
Hash message
Hash check
Public/secret key and signature bytes macros simplification

Adding new route fix
Fix of the hosts to string function
Message trace 'from' inclusion
Fixed encoded message handling

README renamed to README.md
Peer functions renaming
	nonces_get_first to nonces_get_oldest
	nonces_get_last to nonces_get_newest
Inversed conditions, swapped branches
More effective parity check
Initial value of identity's nonce halved
Route stale time increased

Shorter NULL/zero conditions
Switch to libsodium random number generator
Fix of linkedlist_apply_if for no/false predicates
Fix use-after-free in linkedlist_move
Fix edge case memleak in create_p2p_hello
Typos, comments, a little bit of cleaning, etc.

* SIGINT is now being handled
* the peers can connect to each other now

* neighbours, peers and linked list functions in alphabetical order
* more functions in the linked list
* the peers are being represented by their own structure
* linkedlist of pending_neighbours and peers for the next commit