Adding the LPIPS metrics

[RebornForPower]

I have add the lpips metrice by referring the #367

[RebornForPower]

editing the __init__.py and adding the lpips.py file which can be supported by the ymal file to test

[xinntao]

@RebornForPower Thanks for the contribution:-)

As LPIPS takes torch tensors as inputs， we may need to directly pass torch tensors into this metric.

Let me think about it and it may involve the modification to the metric mechanism.

[RebornForPower]

@RebornForPower Thanks for the contribution:-)

As LPIPS takes torch tensors as inputs， we may need to directly pass torch tensors into this metric.

Let me think about it and it may involve the modification to the metric mechanism.

why not process the img into tensor in the calculate function?

[lgtm-com]

This pull request introduces 1 alert when merging a74fb57 into 4d34d07 - view on LGTM.com

new alerts:

• 1 for Unused local variable

[lgtm-com]

This pull request introduces 1 alert when merging 10f55c8 into 4d34d07 - view on LGTM.com

new alerts:

• 1 for Unused local variable

[lgtm-com]

This pull request introduces 1 alert when merging 556909d into 4d34d07 - view on LGTM.com

new alerts:

• 1 for Unused local variable