Add Icon Cache and installed Apps check
Add Icon Cache and installed Apps check

The Icon Cache is built on every start, fetching the current icon if it
is not yet stored.
`checkInstalled()` compares the contents of the Applist with the on the
system installed apps, returning a table [titledid] to easily check for
an installed title using `installed[<titleid>]`

no1dead/Plug1n,Wolvan/Homebr3w