[code-reflection] RFR: MNISTDemo split

[Adam Sotona]

MNISTDemo separation of UI

-------------

Commit messages:
 - MNISTDemo split

Changes: https://git.openjdk.org/babylon/pull/333/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=333&range=00
  Stats: 168 lines in 2 files changed: 100 ins; 61 del; 7 mod
  Patch: https://git.openjdk.org/babylon/pull/333.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/333/head:pull/333

PR: https://git.openjdk.org/babylon/pull/333