Update linearize scripts.

Break into two steps:
* Generate hash list
* Build data file(s) from local bitcoind blocks/ directory.

This supports building one large bootstrap.dat, or multiple
smaller blocks/blkNNNNN.dat files.

contrib/linearize/README.md

@@ -1,2 +1,29 @@
-### Linearize ###
-Construct a linear, no-fork, best version of the blockchain.
+# Linearize
+Construct a linear, no-fork, best version of the blockchain.
+
+## Step 1: Download hash list
+
+   $ ./linearize-hashes.py linearize.cfg > hashlist.txt
+
+Required configuration file settings for linearize-hashes:
+* RPC: rpcuser, rpcpassword
+
+Optional config file setting for linearize-hashes:
+* RPC: host, port
+* Block chain: min_height, max_height
+
+## Step 2: Copy local block data
+
+   $ ./linearize-data.py linearize.cfg
+
+Required configuration file settings:
+* "input": bitcoind blocks/ directory containing blkNNNNN.dat
+* "hashlist": text file containing list of block hashes, linearized-hashes.py
+output.
+* "output_file": bootstrap.dat
+      or
+* "output": output directory for linearized blocks/blkNNNNN.dat output
+
+Optional config file setting for linearize-data:
+* "netmagic": network magic number
+