Crush PNGs to reduce overall size (#7954)

app/javascript/images/elephant-fren.png

app/javascript/images/mailer/icon_cached.png

app/javascript/images/mailer/icon_done.png

app/javascript/images/mailer/icon_email.png

app/javascript/images/mailer/icon_file_download.png

app/javascript/images/mailer/icon_grade.png

app/javascript/images/mailer/icon_lock_open.png

app/javascript/images/mailer/icon_person_add.png

app/javascript/images/mailer/icon_reply.png

app/javascript/images/mailer/logo_full.png

app/javascript/images/mailer/logo_transparent.png

app/javascript/images/reticle.png

app/javascript/images/void.png

public/android-chrome-192x192.png

public/apple-touch-icon.png

public/badge.png

public/mstile-150x150.png

public/web-push-icon_expand.png

public/web-push-icon_favourite.png