coins: Add PIVX

No CSV or segwit.
sethdseed requires a fully synced chain, manual intervention required to set a key derived from the master mnemonic.
Requires a pivxd version with a backported scantxoutset command.

tests/basicswap/test_run.py

@@ -64,6 +64,7 @@ class Test(BaseTest):
     def setUpClass(cls):
         cls.start_ltc_nodes = True
         cls.start_xmr_nodes = False
+        cls.start_pivx_nodes = False
         super(Test, cls).setUpClass()
 
         btc_addr1 = callnoderpc(1, 'getnewaddress', ['initial funds', 'bech32'], base_rpc_port=BTC_BASE_RPC_PORT)