net: implement the necessary parts of the I2P SAM protocol

Implement the following commands from the I2P SAM protocol:

* HELLO: needed for all of the remaining ones
* DEST GENERATE: to generate our private key and destination
* NAMING LOOKUP: to convert .i2p addresses to destinations
* SESSION CREATE: needed for STREAM CONNECT and STREAM ACCEPT
* STREAM CONNECT: to make outgoing connections
* STREAM ACCEPT: to accept incoming connections

Author: vasild

src/Makefile.am

@@ -148,6 +148,7 @@ BITCOIN_CORE_H = \
   fs.h \
   httprpc.h \
   httpserver.h \
+  i2p.h \
   index/base.h \
   index/blockfilterindex.h \
   index/disktxpos.h \
@@ -315,6 +316,7 @@ libbitcoin_server_a_SOURCES = \
   flatfile.cpp \
   httprpc.cpp \
   httpserver.cpp \
+  i2p.cpp \
   index/base.cpp \
   index/blockfilterindex.cpp \
   index/txindex.cpp \