5/7/15 - File Manager UI Improvements

In order to prepare for the Career Center Tech Expo, I hammered out some improvements to our rudimentary file interface.  Before, the app would display all the files on the (emulated) SD card, which for some reason included a bunch of temp files for the emulator.  I first added logic to only show files with paths that matched the regular expression /librifox\/.*/, which only shows files that have librifox/ in the path. Next, I refactored our enumeration handler by pulling all the file traversal logic into a base method that takes functions func_each for code to be executed for each match, func_done for code to be executed once all the files had been traversed, and func_error for any errors that occurred.

This is a really flexible way to implement an algorithm that has slight variations in how it works, as I can display all the librifox files in a list view and delete all librifox files with the exact same call pattern, just by varying the functions passed as func_each and func_done.

Also, because functions keep the scope they were originally called by, I was able to do the following to check whether any librifox files were present on the device: I'm really glad I'm reading JavaScript: the Good Parts :)

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I thought that this was something unique to javascript, but it works in ruby as well! Neat!