Bugfix: DirectX effect files used sampler states in wrong order.

Sampler info stores textureSlot and samplerSlot separately.
SamplerStateInfo._dirty is true per default to always create a sampler state.
Rebuilt stock effects.
Incremented MGFX version.
Bugfix: SamplerStateInfo._dirty must always be set when a property is changed.
Merge remote-tracking branch 'test/samplerfix' into stable_BtA
Merge pull request #1461 from DigitalRune/samplerfix

Bugfix: DirectX effect files used sampler states in wrong order.
Merge branch 'develop' into stable_BtA