Add viewBox to app icons

If we don't add a viewbox a lot of browsers will just say NOPE!!! when we ask them to scale.
nextcloud · LukasReschke · Aug 17, 2016 · Aug 17, 2016 · Aug 17, 2016 · Aug 17, 2016
commit a3c5aefc96c8e4b75e9cfb0f25096f5a5d8f7023
diff --git a/apps/comments/img/comments.svg b/apps/comments/img/comments.svg
diff --git a/apps/files_external/img/app.svg b/apps/files_external/img/app.svg
diff --git a/apps/files_sharing/img/app.svg b/apps/files_sharing/img/app.svg
diff --git a/apps/files_trashbin/img/app.svg b/apps/files_trashbin/img/app.svg
diff --git a/apps/files_versions/img/app.svg b/apps/files_versions/img/app.svg
diff --git a/apps/systemtags/img/app.svg b/apps/systemtags/img/app.svg
diff --git a/apps/testing/img/app.svg b/apps/testing/img/app.svg
diff --git a/apps/user_ldap/img/app.svg b/apps/user_ldap/img/app.svg
diff --git a/core/img/default-app-icon.svg b/core/img/default-app-icon.svg