fixed: include boost header as necessary

Without this include, sometimes BOOST_VERSION was defined and sometimes
it was not, depending on which includes came before it. The result was a
random mix of sleep or sleep_for for boost versions >= 1.50.
fixed: don't use thread::sleep_for where it's known to be broken

Fixes #2690.
Initialize database before checking changed txindex

In case no database exists yet, and -txindex(=1) is passed, we currently first
check whether fTxIndex differs from -txindex (and ask the user to reindex in
that case), and only afterwards initialize the database. By swapping these
around (the initialization is a no-op in case the database already exists),
we allow it to be born in txindex mode, without warning.

That also means we don't need to check -reindex anymore, as the wiping/reinit
of the databases happens before checking.
Fix build date for from-tarball builds
Fix Gnome bitcoin: URI handler
README for contrib/debian
Log reason for non-standard transaction rejection