Unvivtool

* De/Encoder: improved filesystem behavior, especially on ancient Windows
* Decoder: add overwrite mode (auto rename existing files)
* Decoder: create non-existing output directory
* Decoder: never overwrite archive
* CLI: passing an output directory to decoder is optional, and it need not exist
* CLI: command-line options ``-dnl`` ``-i`` ``-f`` ``-fmt`` and their respective arguments are no longer separated by whitespace (breaking change)
* Python: easy installation via ``python -m pip install unvivtool`` on Win, Linux, and macOS

* CLI: drag-and-drop multiple files onto the executable to encode them into a VIV archive
* CLI: drag-and-drop a VIV/BIG archive onto the executable to decode it
* Decoder: skips invalid files instead of erroring out

* unvivtool: add Windows 98 compatibility
* Python: native print

+ De/Encoder: fully support non-printable filenames in archive (represent as Base16/hexadecimal)
+ De/Encoder: set fixed directory entry length
+ CLI: decoder optionally writes re-encode command to _path/to/input.viv.txt_
+ Format: support _BIGH_
+ Format: support _BIG4_ (experimental)

* support up to 214748363 files in archive

* support UTF8-filenames in BIGF archives (e.g., CJK)
* improved decoder (better support for manipulated or "locked" archives)
* improved usability: on Windows, drag-and-drop archives on executable for easy decoding
* improved stability