Update pip in Dockerfiles

pip is now automatically updated to the latest version when you build your app with fbs's Docker integration. See #210. Thank you to @whattheserver for the PR!

Fix mistake in .desktop files on Linux

See #202. Thank you @josh-richardson for the PR!

Fix `fbs installer` on macOS Catalina

Thanks @lune and @komodovaran!

Fix problems with PyInstaller 3.6

fbs is incompatible with PyInstaller 3.6 (see #169). This release fixes the problem by pinning fbs's required PyInstaller version to 3.4. So when you now do

pip install fbs

Then this installs PyInstaller 3.4 (previously, it installed 3.6).

Implement code signing on Windows

For instructions, please see the new section on code signing in the Manual.

Fix problems when both PyQt5 & PySide2 are available

This is a backwards-incompatible release. To upgrade to it, replace the following import:

from fbs_runtime.application_context import ApplicationContext

by one of the following two:

from fbs_runtime.application_context.PyQt5 import ApplicationContext
# or:
from fbs_runtime.application_context.PySide2 import ApplicationContext

Explanation

Earlier fbs versions had the following code:

try:
    from PyQt5 import ...
except ImportError:
    from PySide2 import ...

This lead to problems when you had both PyQt5 and PySide2 installed:

1. PyInstaller packaged both (!) libraries because it saw both imports.
2. The above made fbs always use PyQt5. But if your app uses PySide2,
   then PySide2 and PyQt5 classes / code would be mixed.
3. It wasn't clear (or deterministic, really) which Python binding took
   precedence. For instance, PyQt5 and PySide2 set different QML search paths.
   See #114.

To fix these problems, the above code was split into separate files: One that
contains all PyQt5 imports, and another that contains all PySide2 imports. You
are supposed to import precisely one of the two. This makes PyInstaller
only package the one necessary library, and prevents the above problems.

Please note that actually, PyInstaller 3.4 is not yet smart enough to do 1).
However, recent development versions of it (eg. revision 9e1f05ba2) can do this.

Until PyInstaller 3.5 is out, the best workaround to avoid all of these problems
is to simply not have both PyQt5 and PySide2 installed in your virtual environment
when using fbs.

Fix problems with filtering of Installer.nsi on Windows

See #112.

Give better error messages on unsupported Linux distributions

See #89 and #53. Instead of the exceptions mentioned there, fbs now says "Your Linux distribution is not supported, sorry. You can run fbs buildvm followed by fbs runvm to start a Docker VM of a supported distribution."

Add support for PySide2 5.12.3

Fixes #109

Fix icon-related errors during `freeze` on Mac (Yosemite)

The error was:

iconutil[2088] <Error>: ImageIO: _CGImageDestinationCreateWithWriter capacity parameter (14) is too large for this file format (max is 10)