Add a line with status explanation

[mromanello]

@pletcher Just an idea, let's discuss
As a user, it'd be useful to know (at a glance), at all times, how many glosses are available for the text section in focus and how many am I currently viewing (e.g., as a result of filtering).

Possible template: Currently displaying X glosses from X commentaries for this section (lines x-y). In total, there are Y glosses (of which Z are lemma-less).

Once #20 is fixed, quite a bit of space will be freed up in the top horizontal part (i.e. above the horizontal grey lines)., so this could be easily added.

[mromanello]

Now that the Filter glosses by commentary displays the counts, I believe this would be redundant.