Merge branch 'v4' of twbs/bootstrap/v4 into v4

docs/dist/svg/check.svg

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+	 viewBox="0 0 612 792" enable-background="new 0 0 612 792" xml:space="preserve">
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+</svg>

docs/dist/svg/chevron-left.svg

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+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
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+</svg>

docs/dist/svg/chevron-right.svg

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+<!-- Generator: Adobe Illustrator 18.1.1, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg version="1.1" id="Chevron_right" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px"
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+</svg>

docs/dist/svg/cross.svg

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+<svg version="1.1" id="Cross" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
+	 viewBox="0 0 612 792" enable-background="new 0 0 612 792" xml:space="preserve">
+<path display="none" d="M444.8,544.4c-15,14.4-39.2,14.4-54.2,0L306,451.7l-84.6,92.7c-15,14.4-39.2,14.4-54.2,0
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+</svg>

docs/dist/svg/magnifying-glass.svg

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+<!-- Generator: Adobe Illustrator 18.1.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg version="1.1" id="Magnifying_glass" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px"
+	 y="0px" viewBox="0 0 20 20" enable-background="new 0 0 20 20" xml:space="preserve">
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+</svg>

docs/dist/svg/menu.svg

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+<!-- Generator: Adobe Illustrator 18.1.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg version="1.1" id="Menu" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
+	 viewBox="0 0 20 20" enable-background="new 0 0 20 20" xml:space="preserve">
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+</svg>

docs/dist/svg/warning.svg

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+<!-- Generator: Adobe Illustrator 18.1.1, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg version="1.1" id="Warning" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
+	 viewBox="0 0 20 20" enable-background="new 0 0 20 20" xml:space="preserve">
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+</svg>