Theme the tray menu, move tabs with Ctrl + scroll and smooth wheel switching

[leafOfTree]

• Alt+F leader: tab selection by letter now defaults to Alt+F instead of Alt+S. It is still off by default, and saved shortcuts are kept.
• Themed tray menu: the tray icon's menu uses the same themed menu as the tab menu, in light and dark, instead of the system's light menu.
• Ctrl + scroll: over the tab bar, moves the current tab one place per notch and stops at either end. It can be turned off on the Shortcuts page.
• Smoother scrolling: switching tabs by scrolling counts one tab per wheel notch, including notches a high-resolution wheel or touchpad sends in parts. Every notch of a quick turn is kept, each tab is shown for a moment on the way, and turning back drops the steps still waiting.
• Shortcuts page: number switching, which is on by default, now comes before the opt-in leader key. "Esc" and "tab bar" match the wording elsewhere. The notes under the next/previous tab shortcuts are gone. The view file is renamed to HotKeyView.fs.

Tried in the Release build. Tests cover the Alt+F default, TabNavigation stepping, notch counting and tab moves, and the Ctrl + scroll default.