Updated the version from 1.1 to 1.2
Renamed the header to "Slint Royalty-free Desktop, Mobile, and Web Applications License"
Added definition of "Mobile Application" and grant of right
Moved "Limitations" to 3rd section and "License Conditions - Attributions" to 2nd section
Added flexibility to choose between showing "MadeWithSlint" as a dialog/splash screen or on a public webpage
Moved the para on copyright notices to section under "Limitations"
Some property need to be known at compile time. We already had checks
that the binding is a compile time constant, but there was no check to
prevent, say
self.row = 42;
which wouldn't work or could even cause panic or miscompilation of
generated code
Closes#4037
