Zoom/Crop into selection via brush selection

[cornhundred]

Allow users to selection section of the heatmap to zoom into.

~~Do not actually crop into this section, but just zoom in. Need to be careful about tracking zoom with this function.~~ ~~Also, improve camera resetting, ideally reset camera after zooming/panning event is over.~~

I'm going to probably just make this work through cropping. I'll build a general method to remake the entire viz based on filtering for an arbitrary set of rows/columns (dendrogram will not be shown, rearrange buttons will either be deactivated or reflect on-the-fly calculations). This general filter network method will be built off this method (https://github.com/MaayanLab/clustergrammer/blob/master/src/network/filter_network_using_new_nodes.js) and will be generalized to support dendrogram cropping, crop to zoomed area, and zoom into selection.

• get arbitrary network row/col filtering working
• set up SVG brush crop similar to brush_crop_matrix
  • need to do the algebra to find selected rows/cols on brushing