Add datagram options to `SessionOptions`

[altonen]

Allow user to specify datagram options in SessionOptions:

[PORT=$port]                         # Required for DATAGRAM* RAW, invalid for STREAM
[HOST=$host]                         # Optional for DATAGRAM* and RAW, invalid for STREAM
[FROM_PORT=nnn]                      # SAM 3.2 or higher only, default 0
[TO_PORT=nnn]                        # SAM 3.2 or higher only, default 0
[PROTOCOL=nnn]                       # SAM 3.2 or higher only, for STYLE=RAW only, default 18
[HEADER={true,false}]                # SAM 3.2 or higher only, for STYLE=RAW only, default false

[sjlgasnier]

If I understand the docs correctly, there should be 2 structs : PrimarySessionOptions and SubSessionOptions.
The options listed above should be specified in the latter struct.
The I2CP options must be specified in the former though (some of them are already, like num_inbound, but the other ones could be added as well).

Would such refactoring be ok as a PR ?

As per the docs :
"Do not set the PORT, HOST, FROM_PORT, TO_PORT, PROTOCOL, LISTEN_PORT, LISTEN_PROTOCOL, or HEADER options on a primary session. You may not send any data on a PRIMARY session ID or on the control socket. All commands such as STREAM CONNECT, DATAGRAM SEND, etc. must use the subsession ID on a separate socket.
The PRIMARY session connects to the router and builds tunnels. When the SAM bridge responds, tunnels have been built and the session is ready for subsessions to be added. All I2CP options pertaining to tunnel parameters such as length, quantity, and nickname must be provided in the primary's SESSION CREATE."

[altonen]

Modifying SessionOptions should be enough. From specification for SESSION CREATE:

SESSION CREATE
STYLE={STREAM,DATAGRAM,RAW,DATAGRAM2,DATAGRAM3} # See below for DATAGRAM2/3
ID=$nickname
DESTINATION={$privkey,TRANSIENT}
[SIGNATURE_TYPE=value] # SAM 3.1 or higher only, for DESTINATION=TRANSIENT only, default DSA_SHA1
[PORT=$port] # Required for DATAGRAM* RAW, invalid for STREAM
[HOST=$host] # Optional for DATAGRAM* and RAW, invalid for STREAM
[FROM_PORT=nnn] # SAM 3.2 or higher only, default 0
[TO_PORT=nnn] # SAM 3.2 or higher only, default 0
[PROTOCOL=nnn] # SAM 3.2 or higher only, for STYLE=RAW only, default 18
[HEADER={true,false}] # SAM 3.2 or higher only, for STYLE=RAW only, default false
[sam.udp.host=hostname] # Datagram bind host, Java I2P only, DATAGRAM*/RAW only, default 127.0.0.1
[sam.udp.port=nnn] # Datagram bind port, Java I2P only, DATAGRAM*/RAW only, default 7655
[option=value]*

Currently yosemite is missing all datagram-related options from SessionOptions so they need to be added and since primary, sub, and normal sessions are all created the same way, SessionController must add the appropriate options from SessionOptions to the SESSION CREATE message it's calling SessionController::create_session(). That is, this code https://github.com/altonen/yosemite/blob/cacba2a6925c0ad1d1921eb98ec4da3c5f3cb553/src/proto/session.rs#L170-L186

must match on parameters.style and if it's Repliable/Anonymous, it needs to add the datagram parameters to the SESSION CREATE request

[altonen]

#11