use he init when using relu activations

See merge request toar/mlair!273

added prelu activation, alpha dropout is used for selu act, FCN_64_32_16 is now an inheritance of FCN class

FCN activation name now works with relu

See merge request toar/mlair!270

FCN class can use any layer configuration

See merge request toar/mlair!269

FCN can use an explicite layer configuration, activation layers are now named according to the act fct

catch if regularizer is None but as string

See merge request toar/mlair!268

FCN supports dropout and l1/l2 regularization

See merge request toar/mlair!267

custom objects were missing

See merge request toar/mlair!266

new var loss and custom loss methods

See merge request toar/mlair!265

Resolve "DefaultDataHandler: dask.compute() before dump to file"

Closes #288

See merge request toar/mlair!263

log clim skill scores too

See merge request toar/mlair!262

minor fix to skip calculate error metrics if external data is none

See merge request toar/mlair!261

addendum to FCN class

See merge request toar/mlair!260

Resolve "store performance measures"

See merge request toar/mlair!257

Resolve "create FCN model class"

See merge request toar/mlair!255

Merge branch 'lukas_issue284_feat_create-fcn-model-class' into 'lukas_issue286_feat_performance-measures'

Lukas issue284 feat create fcn model class

See merge request toar/mlair!258