Create new BlockPolicyEstimator for fee estimates

This class groups transactions that have been confirmed in blocks into buckets, based on either their fee or their priority.  Then for each bucket, the class calculates what percentage of the transactions were confirmed within various numbers of blocks.  It does this by keeping an exponentially decaying moving history for each bucket and confirm block count of the percentage of transactions in that bucket that were confirmed within that number of blocks.

-Eliminate txs which didn't have all inputs available at entry from fee/pri calcs

-Add dynamic breakpoints and tracking of confirmation delays in mempool transactions

-Remove old CMinerPolicyEstimator and CBlockAverage code

-New smartfees.py

-Pass a flag to the estimation code, using IsInitialBlockDownload as a proxy for when we are still catching up and we shouldn't be counting how many blocks it takes for transactions to be included.

-Add a policyestimator unit test

qa/rpc-tests/util.py

@@ -33,7 +33,7 @@ def check_json_precision():
     if satoshis != 2000000000000003:
         raise RuntimeError("JSON encode/decode loses precision")
 
-def sync_blocks(rpc_connections):
+def sync_blocks(rpc_connections, wait=1):
     """
     Wait until everybody has the same block count
     """
@@ -41,9 +41,9 @@ def sync_blocks(rpc_connections):
         counts = [ x.getblockcount() for x in rpc_connections ]
         if counts == [ counts[0] ]*len(counts):
             break
-        time.sleep(1)
+        time.sleep(wait)
 
-def sync_mempools(rpc_connections):
+def sync_mempools(rpc_connections, wait=1):
     """
     Wait until everybody has the same transactions in their memory
     pools
@@ -56,7 +56,7 @@ def sync_mempools(rpc_connections):
                 num_match = num_match+1
         if num_match == len(rpc_connections):
             break
-        time.sleep(1)
+        time.sleep(wait)
 
 bitcoind_processes = {}