Blank line rendering in text templates

Consider a text template:

```
{{% CONTENT_TYPE: TEXT }}
{{ statement-1 }}
{{ statement-2 }}
{{ statement-3 }}
{{ statement-4 }}
{{ statement-5 }}
```

With data:

```
{
statement-1: "Did she leave?",
statement-3: "Yes.",
statement-5: "So it's time then to start up the interfabric particle degenerator."
}
```

This generates:

```
Did she leave?

Yes.

So it's time then to start up the interfabric particle degenerator.
```

However we desire to consume lines that render as NULL to produce:

```
Did she leave?
Yes.
So it's time then to start up the interfabric particle degenerator.
```

My thoughts were that a line render pragma could be defined:

```
<<% LINE_RENDER : CONSUME_BLANK >>
```

This means: if a processed line (i.e.: a line containing a Mustache declaration) evaluates to blank (as defined by the standard library) then consume the line (i.e.: do not output the empty content or end of line char).

Start by reviewing the existing text-template rendering behavior described in the issue and the proposed LINE_RENDER: CONSUME_BLANK pragma. Determine how processed lines that evaluate to blank are currently emitted; done means a supported approach produces the three populated lines without intervening blank lines.

Written by the indexing model from the issue text.