Remove "MAX" prefix from model names

[ckadner]

• katalog README (Remove MAX from model names #46)
• model YAMLs name (Remove "MAX" prefix from model names #47)

  name: MAX Image Caption Generator
  model_identifier: max-image-caption-generator
  description: "IBM Model Asset eXchange(MAX) model that generates captions from a fixed vocabulary describing the contents of images in the COCO dataset"

• keep asset IDs for model URLs
• mlx bootstrapper and quickstart catalog_upload.json (Remove "MAX" prefix from model names mlx#224)
• list of models in model-samples/README.md (Update asset list #50)
• rename YAML and MD file names (optional)

FYI @animeshsingh