Doc++
Improved tests for Image, ImageReference and Trade::ImageData classes.

Properly testing copy and move constructors.
Improved BufferImage API, added test.

Move constructor and move assignment now behaves similarly to Image
(not only the buffer but also size is swapped). Added constructor taking
size + data, reordered setData() parameters to match order in Image. The
old setData() function is now alias to the new one, is marked as
deprecated and will be removed in future release.
Added BufferImage&& overloads to *Texture*::set*Image() functions.

The point is that we accept everything except const BufferImage&, as the
buffer needs to be bound, which is not an constant operation, as it
modifies internal GL state tracker.
Simplified and tested Texture move constructor/assignment.

Move constructor and move assignment is now noexcept and it just swaps
the data of the two instances instead of calling GL API, thus it can be
inline. Also removed unneded limitations in BufferTexture.
Ability to print Shader::Type enum to Debug output.
Updated, documented and tested Shader and ShaderProgram movement.

Added Shader::type() and Shader::sources() accessors for testing
purposes, it involved renaming private members (no functional change).
Added missing Framebuffer::id().
Added move constructor/assignment to Framebuffer classes.

Also updated the tests.
Added move constructor/assignment to Query classes.

Also updated the test.
Testing Mesh move constructor and assignment.
Testing Buffer move construction and assignment.
Enabled synchronous debug output for AbstractOpenGLTester.
Fixed GL debug output performance warnings in Buffer test.
Fixed CubeMapTextureArray::image().

This was copypasted from CubeMapTexture and apparently wasn't tested
once. The Coordinate enum is now not needed at all.
Make BufferTexture::id() public.
Added BufferTexture::offsetAlignment() limit query.
Platform: show BufferTexture::offsetAlignment() in magnum-info.
Testing all *Texture functionality.
Added no-op fallback for unsupported EXT_texture_filter_anisotropic.

This extension is ubiquitous, but to make users' life even easier we
now provide no-op fallback for both Sampler::maxAnisotropy() and
Texture::setMaxAnisotropy().