setgenerate creates multiple blocks in -regtest mode

I'm writing some wallet regression tests using -regtest mode, and
need to generate an initial multi-hundred-block chain. Repeatedly
calling setgenerate to generate one block is slow and doesn't
work properly, because block creation happens asynchronously.

This adds two features to setgenerate in -regtest mode:

1) Instead of being interpreted as number of threads to start, the
third argument is the number of blocks to generate.

2) setgenerate will not return until the block creation threads
have created the requested number of blocks.
cleanup error message consistency

  relicts from the CTransaction refactor.
Merge pull request #3300

848fe68 cleanup error message consistency (Julian Langschaedel)
contrib: add sipa's github-merge script
Merge pull request #3302

e5adec3 contrib: add sipa's github-merge script (Wladimir J. van der Laan)
Merge pull request #3294

c8b7425 setgenerate creates multiple blocks in -regtest mode (Gavin Andresen)
Fix uninitialized variable added in b33b9a6fe

After discussing with BlueMatt, this appears to be harmless in its
current state since it's always set before it's used. Initialize it
anyway for readability and future safety.
Merge pull request #3316

106f133 Fix uninitialized variable added in b33b9a6fe (theuni)
Merge branch 'master' of https://github.com/bitcoin/bitcoin
Drop fees by 10x due to the persistently higher exchange rate.

The last fee drop was by 5x (from 50k satoshis to 10k satoshis)
in the 0.8.2 release which was about 6 months ago.

The current fee is (assuming a $500 exchange rate) about 5 dollar
cents. The new fee after this patch is 0.5 cents.

Miners who prefer the higher fees are obviously still able to
use the command line flags to override this setting. Miners who
choose to create smaller blocks will select the highest-fee paying
transactions anyway.

This would hopefully be the last manual adjustment ever required
before floating fees become normal.