Break apart lines

[shreevatsa]

Sometimes a line can span multiple lines, and right now there's no way to insert a line break within a line.

We could either:

• Change schema to have a line be a <p>, so that it contain line breaks internally.
• Allow re-drawing lines and re-doing OCR (#8).

[shreevatsa]

Ouch, notice this giant "line" (because of the X):

(Google OCR result for the same page as previous comment; the screenshot in previous comment was from Tesseract)

[shreevatsa]

Now that we have individual words in line.attrs, we could in principle re-form lines. (What to do with changed text though?)

[shreevatsa]

This line is because of the various dots I think:

So instead of something operating on line.attrs.words, may be better to just implement spliting manually (#8).

(Also because we may get rid of line.attrs.words: #21.)