New VQ-Layer Features: Fixes for Replacement-Feature, PCA-based Lookup

[FlorianPfisterer]

A thorough review of the PCA-based lookup feature should not be necessary, as this has already been done in PR #81.

[Simsso]

Two suggestions concerning documentation:

• The README.md in the resnet_base folder should be updated
• The README.md should be extended by a list of all flags (name, default value, description, file where they appear)

[Simsso]

Before merging, let's

• test the installation and main file once more
• make a decision on the deletion of this file
• write down a list of all flags which are in use
• update the README if necessary