[CB-2649] fix, removes app temp directory name generation based on the CordovaExtension getAppID method, and replaces it with random generation. Also catches offending exception with appropriate error message logging
[CB-2649] ammended solution: includes Absolute Value function wrapper, preventing negative values for directory names, as - symbol was causing a crash
CB-2167 added File.slice action handler

broken commit
[CB-2167] implemented file slice for readAsText, mobile spec tests passing
[CB-2167] implemented file slice for readAsDataURL
[CB-2167] removed dead code from slice wild goosechase, removed debugging statements