Fix Dependency issues

[rs3c]

There are quite a few deprecated dependencies. Let's see if we can update them to newer versions - there might be some code changes involved.
Also on #69 there was a Warning:

Launching lib/main.dart on sdk gphone64 x86 64 in debug mode...
warning: [options] source value 8 is obsolete and will be removed in a future release
warning: [options] target value 8 is obsolete and will be removed in a future release
warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.
3 warnings
warning: [options] source value 8 is obsolete and will be removed in a future release
warning: [options] target value 8 is obsolete and will be removed in a future release
warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.
3 warnings
warning: [options] source value 8 is obsolete and will be removed in a future release
warning: [options] target value 8 is obsolete and will be removed in a future release
warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.
3 warnings
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

This should be a dependency problem as well.