ISOProperties no longer needs its hack to refresh the game list, the
new INI Modified event can be used instead.

Should make loading cached Wii games that lack banners slightly faster.

titles.txt is read into a map and passed to the GameListItem
constructor, making game list scanning a bit more efficient.

ISOPropreties's constructor is changed to take a GameListItem as an
argument instead of creating one on its own, because ISOPropreties
doesn't have the titles.txt map that the GameListItem constructor wants.

The custom title reading code is moved so that custom titles are
returned by GameListItem::GetName(). The comparison code is changed
to use GetName() instead of GetName(DiscIO::IVolume::ELanguage).

GetName(DiscIO::IVolume::ELanguage) must not return custom titles,
because netplay relies on it returning the same name for all players.

DolphinWX: Don't use IsElfOrDol outside of ISOFile

It's redundant because GetPlatform can do the same thing.

HBC uses files named icon.png for icons. This change makes Dolphin
support that file name, and also [executable file name].png
in case someone wants to have multiple files in one folder.

The HBC banner support is mainly intended for DOL and ELF files,
but it can also be used to override banners of disc images,
something that wasn't possible in the past.

There are currently issues with banner scaling not preserving
the aspect ratio and looking bad in general.

Fixed a TON of structuring, formatting.

removed README.txt files from themes at MaJoR's request

Added platform icon for ELFs/DOLs

Games without banners were not cached before, because a banner could
become available at any time, making the cache outdated without it
becoming invalidated. Instead of not caching anything, this change makes
Dolphin check for a banner every time a cache that lacks a banner is read.
This is faster than reading all metadata, because reading a Wii banner
only reads from the game's save file, not the volume and its filesystem.

The cache revision is incremented, because otherwise banners will be
missing if a cache without a banner is created in the new version and
the user switches to an old version and creates a savefile.