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