Updated Android templates

[harry-cpp]

Important notes:

• By default sets API 21 (Android 5.0) as the minimal version, there is nothing stoping you from switching to a lower API if you need it.
• No splash screen for extra speed, also its not really a good policy to use just one image for a splash screen, and also there are multiple ways to make splash screens for Android depending on what you want so... no splash screen.

[stromkos]

Could you include the API changes into the documentation page for consistency? https://github.com/MonoGame/MonoGame/blob/develop/Documentation/android.md

[harry-cpp]

Could you include the API changes into the documentation page for consistency? https://github.com/MonoGame/MonoGame/blob/develop/Documentation/android.md

Hmm... looking at that page, that page is totally misleading.

[Jjagg]

Thanks @cra0zy!