Improve handling of stored 3D views

[marklescroart]

There are a number of improvements that could (should) be made to the handling of 3D views:

(1) Implement standard views for all subjects (top, bottom, front, back, left, right, more) that are available by default

(2) Implement some way to select standard views / save new views in the GUI

(3) Implement tab completion for save_view(), get_view() methods for the handle that webgl.show returns (the functions are currently there, but can't be tab-completed, and so are difficult to discover)

(4) Implement display of extant views as transforms can be displayed (cx.db..transforms prints a list of transforms; cx.db..views throws an error, even if there are views available.