path config problem in detection adaption stage

[ZiangYan]

In detection adaption stage, $WSL_ROOT/det_adapt.sh run a python script named train_net.py, which should be located at $WSL_ROOT/tools/train_net.py. Actually this python script is located at $WSL_ROOT/tools/extra/train_net.py, which caused No such file or directory error.

What's more, $WSL_ROOT/tools/extra/_init_paths.py also assumes $WSL_ROOT/tools/extra/*.py should be in $WSL_ROOT/tools/*.py, otherwise $WSL_ROOT/lib/fast_rcnn cannot be imported.

So there are 2 alternative ways to fix:

1. move all python scripts in $WSL_ROOT/tools/extra/*.py to $WSL_ROOT/tools/*.py
2. fix $WSL_ROOT/tools/extra/_init_paths.py and $WSL_ROOT/det_adapt.sh

Thanks