reuse inner conv

[matpalm]

the v1.0 release code is clumsy and even though we have cycles left we can't add another conv.

but we can reuse one using tied weights

so we instead of training input -> conv0 -> output we could train ``input -> conv0 -> conv0 -> output` by just reusing qconv layer which will train with tied weights, then at inference time we just need 1 additional activation cache and the ability to switch in/out for the inner cache ( which i guess is done with registering? )