_s: Simplify entry meta output

- Fix entry-footer inconsistency between content-*.php files
- Move in a function <code>_s_entry_meta()</code> to avoid duplication

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At the moment there is an inconsistency between content.php and
content-single.php regarding the .entry-footer output.

In my opinion content.php output is would be better to use because it's
easier to translate and allow more customisation.

Finally by moving it into <code>inc/template-tags.php</code> we are
getting rid of some duplicated code.
_s: Update to entry meta output. See #537

* Rename function
* Move edit link outside of function
* Remove comments link on single post
Add hidden post title to the continue reading link
Merge pull request #516 from chrisdc/continue_reading_link

Add post title to the continue reading link for context.
_s: Move edit link in template tag for consistency

Every time `_s_entry_footer()` is used, it’s followed by
`edit_post_link()`. Might as well just move that back in the template
tag.
_s: Update pot file to reflect changes.
Merge branch 'Entry-Meta-Output' of https://github.com/Automattic/_s into Entry-Meta-Output

Conflicts:
	content-single.php
Merge branch 'Entry-Meta-Output'