Update a few library projects to target v8.1

Update a few library projects to target v8.1

[Notepad] Bump TargetFrameworkVersion to v10.0

[Button] Add uses-sdk to manifest

[recyclerview] better OO, formatting (#310)

fixes https://github.com/MicrosoftDocs/xamarin-docs/issues/1372

Update minSdkVersion for projects using support lib (#309)

API 16 is the lowest version of Android that is officially supported by
Xamarin.Android. In most cases, this restriction is only presented as a
build warning. Recent changes to use Google's [manifest merger tool][0]
have however surfaced a new error in projects which use the support
libraries and specify a minSdkVersion lower than API 14. These projects
should be updated to use a minSdkVersion of 16 to avoid both this new
error, and the existing warning about using an unsupported minimum SDK
version.

[0]: dotnet/android@2c6f5cd

Update minSdkVersion for projects using support lib (#309)

API 16 is the lowest version of Android that is officially supported by
Xamarin.Android. In most cases, this restriction is only presented as a
build warning. Recent changes to use Google's [manifest merger tool][0]
have however surfaced a new error in projects which use the support
libraries and specify a minSdkVersion lower than API 14. These projects
should be updated to use a minSdkVersion of 16 to avoid both this new
error, and the existing warning about using an unsupported minimum SDK
version.

[0]: dotnet/android@2c6f5cd

Update minSdkVersion for projects using support lib (#309)

API 16 is the lowest version of Android that is officially supported by
Xamarin.Android. In most cases, this restriction is only presented as a
build warning. Recent changes to use Google's [manifest merger tool][0]
have however surfaced a new error in projects which use the support
libraries and specify a minSdkVersion lower than API 14. These projects
should be updated to use a minSdkVersion of 16 to avoid both this new
error, and the existing warning about using an unsupported minimum SDK
version.

[0]: dotnet/android@2c6f5cd

Update minSdkVersion for projects using support lib (#309)

API 16 is the lowest version of Android that is officially supported by
Xamarin.Android. In most cases, this restriction is only presented as a
build warning. Recent changes to use Google's [manifest merger tool][0]
have however surfaced a new error in projects which use the support
libraries and specify a minSdkVersion lower than API 14. These projects
should be updated to use a minSdkVersion of 16 to avoid both this new
error, and the existing warning about using an unsupported minimum SDK
version.

[0]: dotnet/android@2c6f5cd

Update minSdkVersion for projects using support lib (#309)

API 16 is the lowest version of Android that is officially supported by
Xamarin.Android. In most cases, this restriction is only presented as a
build warning. Recent changes to use Google's [manifest merger tool][0]
have however surfaced a new error in projects which use the support
libraries and specify a minSdkVersion lower than API 14. These projects
should be updated to use a minSdkVersion of 16 to avoid both this new
error, and the existing warning about using an unsupported minimum SDK
version.

[0]: dotnet/android@2c6f5cd