Fix for GetBlockValue() after block 13,440,000

Forces the block reward to zero when right shift in GetBlockValue() is
undefined, after 64 reward halvings (block height 13,440,000).
Fix importwallet nTimeFirstKey
[Qt] rescan progress
Edit subsidy_limit_test to account for BIP42

Because no one wants 4 gold mines being discovered every mibillenium.
Have pull-tester run the listtransactions.py regression test

This should show how to run a python-based regression test
successfully in the pull-tester environment.
Merge pull request #3842 from ditto-b/master

Fix for GetBlockValue() after block 13,440,000
Merge pull request #3928

3927836 [Qt] rescan progress (Cozz Lovan)
Merge pull request #3998

cb4bdd1 Have pull-tester run the listtransactions.py regression test (Gavin Andresen)
Merge pull request #3929

4c35366 Fix importwallet nTimeFirstKey (Cozz Lovan)