pycatsearch

Urgent release to fix file dialogs not showing up.

Less important changes:
- fixed that ugly 99% progress at the end of downloading catalog data,
- refactored Preferences dialog to make it smaller,
- added icons from [`qtawesome`](https://github.com/spyder-ide/qtawesome) if it's installed,
- added an option to ignore a new version and not to warn about it.

Added _Check for Updates_ action in _Help_. With some luck, this will check for updates and install them if ones found.

The filling of the results' table became some 9 times faster.

Moreover, if the `orjson` package is available, it's used to load the catalog data instead of the built-in `json`. With `orjson`, the loading is almost twice faster. It's half a second benefit, but it's better than nothing.

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.