This automatically picks the right zoom level to make the patch fill the window as much as possible. Also fixes a missing call to pdgui.gui_canvas_get_scroll in the m.view.zoomreset menu command which caused the viewport not to be updated properly after resetting the zoom level in canvas windows.

for garrays we disable editing gl_x1 and gl_x2. They get set automatically to show the entire array by default. May want to revisit array viewport later, but for now this keeps the bug from happening.

* canvas dialog is a bit too complex to have "Cancel" button revert any changes we may have applied. (It's not out of the realm of possibility, but for now it's easier just to use a nonstandard "Close" button to show the discrepancy)
* font dialog updates on change of radio button, so we just need a "Close" button there
* prefs dialog also too complex to do a revert on "Cancel"
* iemguis and gatom properly revert on "Cancel"

use <dialog> modal instead of javascript prompt. Also, port some changes from Vanilla to allow closing window immediately after saving

fix feature for putting array in existing graph
add a delete checkbox for graphs with multiple arrays