Implements missing FlattenerLayer functions.

Signed-off-by: Axel Davy <axel.davy@ens.fr>
Merge pull request #848 from axeldavy/FlattenerLayerComplete

Implements missing FlattenerLayer functions.
Add some missing functions to CompositeLayer

Adapted from the MLP code.
Add missing wrap to layer get_monitoring_channels
CompositeLayer: Take into account routing_needed for get_layer_monitoring_channels
Remove useless [] for any and all
Add a FIXME comment for get_monitoring_channels.
get_lr_scalers: replace float by py_float_types
Improves CompositeLayer get_layer_monitoring_channels readability.
Remove bad warnings.

Laurent and Bart are ok with that.
Use xrange instead of range.
Use parenthesis instead of \, as suggested by dwf
Fix typo
removes useless FIXME