refactoring Menu/MenuItem, subclassing a base Menu
remove Page view, since it only has an update() method, moving update to View
add browse page, change Edit page sample icon
remove Directory, Instrument and SampleFile to massively simplify things - they were bloated and unneeded abstractions that aren't needed now that we have a custom file browsing view
WIP merge DirectoryManager and FileHelper, optimize lists with many files by using null bgIcons unless selected/pressed
add browse icon to root file browse item, fix bug where setting foreground icon on ImageButotn AFTER setting text did not update text offset
filter wav/midi files for respective file menu browsers, handle possible null pointer from listFiles()
fix asset copying
only arm after all tracks are loaded, just to be safe.  fix bug in native wavfile_getSample for tracks loaded from file
fix bug where temp files (.raw) aren't being cleaned up - add Janitor thread to run a finally in onCreate, which avoids the problem of onDestroy killing the process
clean up in onDestroy even if not finishing. add back sample size limit for determining in-memory vs file, fix record directory regression
check if temp (.raw) file exists before copying wav contents to it - if it is, just use another file reference into the existing file
avoiding in-memory copy of wav files by reading directly from file during copy
use for-loop instead of using ftell for every sample
cut wavfile copy reads/writes in half by reading into two-element char array instead of two separate char reads