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

Convert aoti[64] to fromstr, itostr[64] to tostr.
Add Log class (log.{cpp,h}), replaces LogPrintf function.
Remove error(...) function.
Fix functions relying on the false return from error function.
Use fstream where possible (when no fsync is required).
Use boost::format for localized string token replacement.
Add ability to request the translation as a string.
Move time functions from util.{h,cpp} to bitcointime.{h,cpp} (can not use time.h).
Use boost::format instead of ostringstream when possible.