Data_* Cleanup

[bvanessen]

• Input layer output size is grabbed directly from data coordinator
• remove access to the global mini-batch size - all mini-batch buffer sizes are derived
• identify, correct, or deprecate JAG data reader issues that are encumbering process
• multi-key-value input data reader
• remove data_* from everywhere
• callbacks???
• input layer no longer modifies data reader / coordinator state. Move to outside of model
• Get sample indices per mb
• get num iterations per epoch - move to SGB
• The location of shuffle_required should be moved out of data reader metadata