Add functions:

1. Add images batch tracing
2. Add radius estimation of traced neurites (precise when x-,y-,z- resolution ratio of image is 1:1:1)
3. Support large-scale tracing of H5 file. The operation is the same as brain-wide tracing.
4. Add shape reconstruction of neurites in neuron population
5. Support dragging a tif or a swc file into GTree
6. Fix bugs.

The source_code.zip is added by github automatically. It is a useless package. However I do not know how to remove it.