included-tests: update gitian descriptors for hexdump dependency
included-tests: generate binary data from test files for inclusion into test binaries

This change moves test data into the binaries rather than reading them from
the disk at runtime.

Advantages:
- Tests become distributable
- Cross-compile friendly. Build on one machine and execute in an arbitrary
  location on another.
- Easier testing for backports. Users can verify that tests pass without having
  to track down corresponding test data.
- More trustworthy test results and easier quality assurance as tests make
  fewer assumptions about their environment.
- Tests could theoretically run at client/daemon startup and exit on failure.

Disadvantages:
- Required 'hexdump' build-dependency. This is a standard bsd tool that should
  be usable everywhere. It is likely already installed on all build-machines.
- Tests can no longer be fudged after build by altering test-data.
Merge pull request #2985 from theuni/included-tests

Embedded test data in bitcoin_test
Added new config option noautofillkeypool.

One of the most annoying things about trying to maintain wallet backups is the fact that every time you unlock a wallet the key pool gets automatically refilled, thus making any existing backups of the wallet obsolete. The user now has the choice to disable automatic refilling of the keypool by adding the following line to bitcoin.conf:

noautofillkeypool=1

This effectively disables all automatic key generation, requiring the user to manually run keypoolrefill to replenish the wallet when the key pool runs low. It is recommended to call backupwallet immediately after calling keypoolrefill.

If noautofillkeypool is not set in bitcoin.conf, the app defaults to its old behavior thus ensuring full backwards compatibility.
Added ability to refill key pool from Bitcoin-Qt.
Got rid of the wallet default key since it isn't being used at all anymore and only produces bad behaviors in Bitcoin-Qt.