LRP rule coverage for Flux layers

[adrhill]

This issue keeps track of which Flux layers in the model reference got LRP implementations.

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Basic layers

• [x] Dense
• [x] flatten

Convolution

• [x] Conv
• [x] DepthwiseConv
• [x] ConvTranspose
• [x] CrossCor

Pooling layers

• [x] AdaptiveMaxPool
• [x] MaxPool
• [x] GlobalMaxPool
• [x] AdaptiveMeanPool
• [x] MeanPool
• [x] GlobalMeanPool

General purpose

• [ ] Maxout
• [ ] SkipConnection
• [ ] #10
• [ ] Bilinear
• [ ] Diagonal
• [ ] Embedding

Normalisation & regularisation

• [ ] normalise
• [ ] BatchNorm
• [x] dropout
• [x] Dropout
• [x] AlphaDropout
• [ ] LayerNorm
• [ ] InstanceNorm
• [ ] GroupNorm

Upsampling layers

• [ ] Upsample
• [ ] PixelShuffle

Recurrent layers

• [ ] RNN
• [ ] LSTM
• [ ] GRU
• [ ] Recur