Add few more modes for crops

[lext]

Test-time-augmentation would greatly benefit from having 5 crops:

• Left bottom
• Right bottom
• Left top
• Right top
• Center

The current implementation has only c. I propose to add 'lc', 'rb', 'lt','rt', which would enable a strightforward TTA.

[lext]

This may or may not be important, as it is often easier to implement TTA directly in Pytorch 🤔