UI fix: change "select a file" to "select a zip file"

[felciano]

Given the new support for reading the zip file you get from Amazon, it would be nice if the UI clarified that the app has this parsing intelligence, vs the user needing to unzip it and then somehow determine which file to load into the app. An easy fix may be to rename the upload button to "select a zip file" or even "select an Amazon zip file"