Fix crash on v1 timecode files with zero override ranges
Fix moving files to the front of the MRU list
Replace boost::format with agi::format

boost::format is slow to compile, slow to run, and has an unpleasant
interface.
Remove a bunch of unused functionalty from agi::Exception
Replace wxString::Format with agi::format

It's modestly faster and significantly more type-safe. Closes #1733.
Extract some of the string formatter implementation to format.cpp
Use iconv rather than std::wstring_convert

libstdc++ 4.8 does not have <codecvt>.