Various aesthetic changes

Changed two icons, increased speed of mouse zoom, and made color rule
close and swap buttons animate with the main button.
File Dependencies

Implemented functions for determining dependencies and dependents of
files, so that Activating and Deactivating out of order no longer
crashes the program.
Selection Menu Improvements

The handlebar is now correctly boxed so clicking it no longer deselects
nodes.
Separated the data from the node list.
Added remove buttons for deselection, and made it wider to compensate
for lost space.
Basic Terminal Functionality

Implemented a rough terminal and the messaging system for displaying
error/warning messages.
Color by specified node

Fixed using_headers in DataFile.
Added functionality for coloring by individual node
Color by node references Node not Pkey/DataFile

Switched the implementation of node coloring to reference the Node
itself, rather than a pkey and a file pointer. Now when the primary keys
of the file change the rule is not broken.
Miscellaneous improvements

Keyboard control on locked camera, Select All from right click closes
the right click menu, and aesthetic change on selection menu
Multiple selection for Cluster and Node rules

Mirrored the functionality present in source-filtered color rules where
the user can select multiple items at once. Did not implement
attributes.