Remove template matching and pseudo opcodes

The current code contains a rather complex script template matching engine,
which is only used for 3 particular script types (P2PK, P2PKH, multisig).
The first two of these are trivial to match for otherwise, and a specialized
matcher for multisig is both more compact and more efficient than a generic
one.

The goal is being more flexible, so that for example larger standard multisigs
inside SegWit outputs are more easy to implement.

As a side-effect, it also gets rid of the pseudo opcodes hack.

src/script/script.h

@@ -181,13 +181,6 @@ enum opcodetype
     OP_NOP9 = 0xb8,
     OP_NOP10 = 0xb9,
 
-
-    // template matching params
-    OP_SMALLINTEGER = 0xfa,
-    OP_PUBKEYS = 0xfb,
-    OP_PUBKEYHASH = 0xfd,
-    OP_PUBKEY = 0xfe,
-
     OP_INVALIDOPCODE = 0xff,
 };