Manual tweaks on all SVGs

* Gives a consistent header to all images
* Makes future changes easier to see
* Some images slightly smaller
* Some images use SVG2 features (`href`)
* Most images smaller or the same size
* A few images slightly larger

images/svg/slideshare.svg

@@ -1 +1,6 @@
-<svg xmlns="http://www.w3.org/2000/svg" fill="#fff" aria-label="Slideshare" role="img" viewBox="0 0 512 512"><rect width="512" height="512" fill="#1376b4" rx="15%"/><path d="M428 272c-13 24-41 32-70 47v54c0 8-10 53-49 53s-51-23-51-31v-51l-12-4v55c0 8-14 21-33 21s-56-26-56-43v-59s-51-19-63-34c-12-14-18-20-15-27 4-9 42 22 64 27s62 8 78 8c16-1 26 5 35 14l2 1v-7c0-7 21-10 34-10h56c6 0 57-16 69-29s24-10 11 15zm-118-4c22 0 39-17 39-38s-17-38-39-38c-21 0-39 17-39 38s18 38 39 38zm-104 0c22 0 39-17 39-38s-17-38-39-38c-21 0-39 17-39 38s18 38 39 38z"/><path d="M138 86c-25 0-44 20-44 43v144h21V129c0-12 10-22 23-22h236c13 0 23 10 23 22v146h22V129c0-23-20-43-45-43z"/></svg>
+<svg xmlns="http://www.w3.org/2000/svg"
+aria-label="SlideShare" role="img"
+viewBox="0 0 512 512"><rect
+width="512" height="512"
+rx="15%"
+fill="#17B"/><path fill="#fff" d="M138 86c-25 0-44 20-44 43v127c-8-4-14-6-15-3-3 7 3 13 15 27 12 15 63 34 63 34v59c0 17 37 43 56 43s33-13 33-21v-55l12 4v51c0 8 12 31 51 31s49-45 49-53v-54c29-15 57-23 70-47 12-24 2-28-9-17V129c0-23-20-43-45-43H138zm0 21h236c13 0 23 10 23 22v140c-19 9-45 17-49 17h-56c-13 0-34 3-34 10v7l-2-1c-9-9-19-15-35-14-16 0-56-3-78-8-8-2-18-7-28-13V129c0-12 10-22 23-22zm68 85c-21 0-39 17-39 38s18 38 39 38c22 0 39-17 39-38s-17-38-39-38zm104 0c-21 0-39 17-39 38s18 38 39 38c22 0 39-17 39-38s-17-38-39-38z"/></svg>