* use mean as default for benchmark metric; change result representation;
add --all for benchmarking all configs at a time

* fix comments

* add --model_exclude

* pretty print

* improve benchmark result table header: from band-xpu to xpu-band

* suppress print message

* update benchmark results on CPU-RPI

* add the new benchmark results on the new intel cpu

* fix backend and target setting in benchmark; pre-modify the names of int8 quantized models

* add results on jetson cpu

* add cuda results

* print target and backend when using --all

* add results on Khadas VIM3

* pretty print results

* true pretty print results

* update results in new format

* fix broken backend and target vars

* fix broken backend and target vars

* fix broken backend and target var

* update benchmark results on many devices

* add db results on Ascend-310

* update info on CPU-INTEL

* update usage of the new benchmark script

add model path searcher and remove hardwritten file paths from benchmark configs; pack ppresnet, mobilenet & crnn with labels; fix palm det data; add flags to enable models of different precision separately (#123)

* Improve benchmark configurations:

* Move data downloading from configs to download_data.py. Add an alternative download link.

* Add Data class to operate data loading and indexing.

* Add Metric class to operate benchmark runs.

* Benchmark results are now the median or geometric mean of benchmark
  runs.

* benchmark framework: benchmarks based on configs

* added impl and benchmark for YuNet (face detection)

* added impl and benchmark for DB (text detection)

* added impl and benchmark for CRNN (text recognition)