Add commons-io lib for #12.
Restructure Filter library for #12.

+ Use IOUtils for writing.
+ Throw IO errors instead of catching them and ignoring them.
+ Rename NULL_FIL to NULL_FILTER.
Update dumpStdoutAndStderr for #12.
Don't unnecessarily map Enum values for #12.
Modify MainActivity and add TagEnum for #12.

+ Convert input image to RGB using the new Filter interface.
+ Use TagEnum to identify tags.
Set TEMP and TMPDIR for #12.
Use IOUtils to copy filter executables for #12.
s/./_