Use C++ streams instead of C-style printf functions

Convert aoti[64] to fromstr, itostr[64] to tostr.
Add CLogStream (logstream.h), wraps ostringstream but preserved type after insertions.
Use fstream where possible (when no fsync is required).
Change error function to have void return type.
Fix functions relying on the false return from error function.
Use boost::format for localized string token replacement.
Remove LogPrint function, replace with Log class.

Move time functions from util.{h,cpp} to bitcointime.{h,cpp} (can not use time.h).
Remove error(...) function.