Subaddress unit tests

Basic unit test fixture, and initialization of a subaddress account.

Signed-off-by: Cole Lightfighter <cole@onicsla.bz>

tests/unit_tests/CMakeLists.txt

@@ -55,6 +55,7 @@ set(unit_tests_sources
   serialization.cpp
   sha256.cpp
   slow_memmem.cpp
+  subaddress.cpp
   test_tx_utils.cpp
   test_peerlist.cpp
   test_protocol_pack.cpp