Update portfolios.php

Added order and orderby options to the portfolio shortcode
Update portfolios.php

Sanitized orderby option
Update portfolios.php

Mistake in constructing the argument to orderby - argument is now a space separated string rather than an array.
Subscription form: do not display the logged in user's email

Can be overwritten with the jetpack_auto_fill_logged_in_user filter
Fixes #694
Subscriptions: Fix spacing

See https://github.com/jeherve/jetpack/commit/686ed49ceda02d4f49d66f1028a4523e9f882437#commitcomment-6888035
VideoPress: update module description wording

"host" makes it sound like the videos are hosted on your site,
while they're hosted on WordPress.com.
Minileven: update module description

The Mobile Theme is not activated on tablets, just phones.
Allow uppercase arguments to order option

Converts the order option to upper case before checking the value. Allows users to use upper, lower, or a combination in the shortcode and ensures that the argument is uppercased before passed to WP_Query.
Slideshow: Add title and alt text to images

Fixes #1095
Site Icon: Remove trailing whitespace
Social Meta Tags: add Site Logo and Site Icon fallback

When no image is found in a post, use fallbacks to build an Open Graph Image tag and a Twitter Card
Site Icon: the icon should be 512px minimum
Twitter Cards: fallback if there is no existing image card
Nova Menu CPT: fix notice when we have no taxonomies

Notice: Undefined variable: term_id in ...wp-content\plugins\jetpack\modules\custom-post-types\nova.php on line 965
Related Posts: Allow filter by `post_format`

We have added `post_format` into the Elasticsearch index so we can how filter
by that for related posts. By default all post formats are returned however
there is now a `jetpack_relatedposts_filter_post_formats` that can be used like
so:

```php
// Only return image and gallery post formats
function jetpackme_related_post_only_images( $post_formats, $post_id ) {
	$post_formats[] = 'image';
	$post_formats[] = 'gallery';
	return $post_formats;
}
add_filter(
	'jetpack_relatedposts_filter_post_formats',
	'jetpackme_related_post_only_images'
);
```

Resolves #287
Images: Allow a filter to disable image resizing via WPCOM

Allow users to set a `jetpack_images_fit_image_url_override` filter which if
set will be used to determin the url to a resized image. This allows users to
bypass Photon / WordPress.com.

Resolves #1083
Nova Menus: use current instance to maintain object context for static function outside of class
Limited orderby option

Update ensures that the `orderby` option is now limited to `author`, `date`, `title`, `rand` and combinations of these seperated by a comma. Invalid keys are skipped, and a space seperated string is created for passing through to `WP_Query`. The array item is unset if no appropriate values are entered so it will pick up the default in `WP_Query`.
Subscriptions: missing whitespace

See https://github.com/Automattic/jetpack/pull/725/files#r20790518
Plugin Endpoint: return next autoupdate time

Include the next scheduled time for autoupdating in our plugin object.