Mostly-working Hush full node sans Verus!!!

Every line of Verus-specific code has been removed from the codebase.
This code compiles on Linux and can do a partial sync. A full sync
and other extensive tests need to be done before it's merged into
the duke branch.

BUGS:

One known bug is that the node starts to CPU mine by default, lol.

src/Makefile.am

@@ -457,7 +457,6 @@ libbitcoin_common_a_SOURCES = \
   script/cc.cpp \
   script/interpreter.cpp \
   script/script.cpp \
-  script/script_ext.cpp \
   script/script_error.cpp \
   script/sign.cpp \
   script/standard.cpp \