Include usage in retraining wizard

[eacharya]

• When destroying a mini-iteration ensure that any parent references are deleted as well
• Include step-by-step usage instruction in retraining wizard
• Add summary of patches w.r.t. lowest score and number of patches with scores below 0.8 threshold

[eacharya]

Merged to development:

• Issue 33: Add instructions to retraining wizard steps - https://github.com/zigvu/kheer/commit/210a50361a47431eb28d3d8b8d4e1ed7761f8c1c
• Issue 33: Add lowest score to patch selection page - https://github.com/zigvu/kheer/commit/e5c82d44ca3177ee06e08fae8fb148c4a5a14c10
• Issue 33: Add number of patches below threshold to selection page - https://github.com/zigvu/kheer/commit/58288dd69e573c955cc5ca83366e8f9581e3e06b