Pycatsearch

Previously, all the PE files (`pycatsearch.exe`, `pycatsearch-async-downloader.exe`, `pycatsearch-downloader.exe`) were marked as GUI scripts, so no console output appeared. Now, `pycatsearch-async-downloader.exe` and `pycatsearch-downloader.exe` are non-GUI scripts, and `pycatsearch-cli.exe` added to show the output.

To search from a command line:
commandline
pycatsearch --min-frequency 118749 --max-frequency 118751 catalog.json.gz -n oxygen


To download catalog data:
commandline
pycatsearch-downloader --min-frequency 115000 --max-frequency 178000 catalog.json.gz

or
commandline
pycatsearch-async-downloader --min-frequency 115000 --max-frequency 178000 catalog.json.gz


To start the GUI:
commandline
pycatsearch

or
commandline
pycatsearch catalog.json.gz

to load `catalog.json.gz`.

From now on, the code forms a package, which gets published to PyPI.

No significant changes in the behavior made. It's just more convenient to obtain the application.

When several catalog files were loaded, and the search was performed across a frequency range outside the range of a catalog, an error was thrown. That crashed the app. Now, nothing's returned instead.

As a minor change, now the values of the frequency range, the center, and the deviation are corrected to the nearest value instead of discarding the input.

The code looks mature enough to announce the release.