added character image feature (NOT semantic) similarity based reranki…

…ng mode (#7)

* import trying generating charactor feature vector: WIP

* gen_cfeatures.py worked with GPU. with normal GPU, throuput was about 0.09sec/file.

* implemented Similarity index generation to gen_cfeatures.py .

* reverted and modified requimenets files.

* implemented cfeature based reranking version. testing is yet.

* cfeature special mode worked collectly.

* implemented search mode selector to web UI.

* supported + and - operator on query when charactor oriented search mode.

* enhanced web UI to display tags when charactor oriented search mode.