Ability to set base and max mip level on textures.

Curiously this functionality is not available on ES2, just the max limit
is supported by APPLE_texture_max_level extension.
Removed long-deprecated Magnum/Swizzle.h header and Magnum::swizzle().

Use Math/Swizzle.h and Math::swizzle() instead.
Removed long-deprecated ImageFormat.h header, ImageFormat/ImageType enums.

Use ColorFormat.h header, ColorFormat and ColorType enums instead.
Amazingly enough there was a bug in Magnum.h (ColorType was typedef'd to
itself instead of ImageType).
Removed long-deprecated Matrix2 and Matrix2d typedefs.

Use Matrix2x2 and Matrix2x2d instead.
Removed long-deprecated Buffer::set*Data() raw pointer overloads.

Use overloads taking Containers::ArrayReference instead.
Platform: removed long-deprecated InputEvent::Modifier::*Button values.

Use *Event::buttons() and *Event::Button enum instead.
Removed long-deprecated *::maxSupported*() limit queries.

Use alternatives without the "Supported" substring instead.