Optimize png images losslessly via zopflipng

[PeterDaveHello]

22 PNG images are re-compressed losslessly as below:

 app/images/badges_screenshot.png                 | Bin 10433 -> 7025 bytes
 app/images/ctl-logo-white.png                    | Bin 11559 -> 7640 bytes
 app/images/favicons/apple-touch-icon-114x114.png | Bin 13378 -> 10719 bytes
 app/images/favicons/apple-touch-icon-120x120.png | Bin 14209 -> 11277 bytes
 app/images/favicons/apple-touch-icon-144x144.png | Bin 18989 -> 14806 bytes
 app/images/favicons/apple-touch-icon-152x152.png | Bin 21782 -> 16838 bytes
 app/images/favicons/apple-touch-icon-57x57.png   | Bin 4331 -> 3681 bytes
 app/images/favicons/apple-touch-icon-60x60.png   | Bin 4641 -> 3927 bytes
 app/images/favicons/apple-touch-icon-72x72.png   | Bin 6280 -> 5202 bytes
 app/images/favicons/apple-touch-icon-76x76.png   | Bin 6779 -> 5660 bytes
 app/images/favicons/favicon-128.png              | Bin 8368 -> 6710 bytes
 app/images/favicons/favicon-16x16.png            | Bin 817 -> 648 bytes
 app/images/favicons/favicon-196x196.png          | Bin 19441 -> 13905 bytes
 app/images/favicons/favicon-32x32.png            | Bin 1788 -> 1464 bytes
 app/images/favicons/favicon-96x96.png            | Bin 8942 -> 7358 bytes
 app/images/favicons/mstile-144x144.png           | Bin 18989 -> 14806 bytes
 app/images/favicons/mstile-150x150.png           | Bin 54135 -> 41120 bytes
 app/images/favicons/mstile-310x150.png           | Bin 99410 -> 70755 bytes
 app/images/favicons/mstile-310x310.png           | Bin 168605 -> 115515 bytes
 app/images/favicons/mstile-70x70.png             | Bin 8368 -> 6710 bytes
 app/images/grid_line.png                         | Bin 1026 -> 96 bytes
 app/images/logo.png                              | Bin 19707 -> 15257 bytes

[PeterDaveHello]

@rossf7 would you like to take a look please? Thank you!