Do not use C++11 std::vector.data()

std::vector.data() is a C++11 feature that makes my OSX build machine unhappy.
Merge pull request #2297 from sipa/notes

Some improvements to the release notes
Merge pull request #2295 from sipa/tidydir

Add script to clean up datadirs
Merge pull request #2286 from gavinandresen/fix2285

Do not use C++11 std::vector.data()
Change progress bar from block-based to time-based

This is less confusing to most people, and doesn't rely on estimates
of the total number of blocks received from other nodes.
Transactions-based verification progress