Added possibility to save the visual attention for Show, attend and tell architecture as an image. Adjusted axis parameter in softmax layer to ignore batch size. Fixed a problem with some states not being initialized correctly in C++ code due to previous changes to the inline mode

fixed various bugs, in particular to allow integer outputs in C++ code generation and to fix shape errors for LSTM inputs

Renamed VariableSymbol to ParameterSymbol, introduced layer variable declarations, changed IOSymbol to VariableSymbol which now combines IO variables and layer variables and implemented RNN layer