Reduce the amount of magic numbers in JS code in Gallery

[agr]

Gallery JS code is ridden with magic numbers:

NuGetGallery/src/NuGetGallery/Scripts/gallery/common.js

Line 12 in 6136fc9

return parseInt(ua.substring(msie + 5, ua.indexOf('.', msie)), 10);

NuGetGallery/src/NuGetGallery/Scripts/gallery/common.js

Line 244 in 6136fc9

var isInteract = (code === 13 /*enter*/ || code === 32 /*space*/) && !e.altKey && !e.ctrlKey && !e.metaKey && !e.shiftKey;

NuGetGallery/src/NuGetGallery/Scripts/gallery/common.js

Lines 574 to 578 in 6136fc9

	(code >= 48 && code <= 57 // numbers 0-9
	|| code >= 64 && code <= 90 // letters a-z
	|| code >= 96 && code <= 111 // numpad
	|| code >= 186 && code <= 192 // ; = , - . / `
	|| code >= 219 && code <= 222) // [\ ] '

NuGetGallery/src/NuGetGallery/Scripts/gallery/autocomplete.js

Lines 64 to 67 in 6136fc9

	if ((e.keyCode >= 46 && e.keyCode <= 90) //delete, 0-9, a-z
	|| (e.keyCode >= 96 && e.keyCode <= 111) //numpad
	|| (e.keyCode >= 186) //punctuation
	|| (e.keyCode == 8)) //backspace

etc.

For better code readability it would be nice to provide nice names at least for some of them (key codes, for example). Some attempts to do it seems to have been done in the past, we need to extend it:

NuGetGallery/src/NuGetGallery/Scripts/gallery/autocomplete.js

Lines 3 to 13 in 6136fc9

	var _autocompleteTimeout = 0;
	var _autocompleteDelay = 100; // time to wait between keypresses before starting autocomplete requests
	var _resultsCache = {};
	var _maxResults = 9;
	var _lastIndex = 0;
	var _keyCodes = {
	tab: 9,
	esc: 27,
	upArrow: 38,
	downArrow: 40
	};