Improve functionality

Use new method to check if a file exists when creating listfile.
Add new function to try and open files in the wc3 map, showing
the exception on failure.
Use the smaller wc3Files_compact.txt for checking what files exist
in the map.
Initial commit

Smaller variant of wc3Files.txt with most filenames that
are unlikely to be used in a custom map removed.
mpyq refactor, break big class into several files

To improve the readability of the code, mpyq has been
broken into several smaller modules.
Fix #10 by fixing the decryption process for encrypted files.
(Ignore sector index relative to start of file when calculating
the key for a specific sector)