Fix DocumentEngine line behaviors in Diffusion

Summary:
Ref T13105. Fixes some issues with line linking and highlighting under DocumentEngine:

• Adding $1-3 to the URI didn't work correctly with query parameters.
• Reading $1-3 from the URI didn't work correctly because Diffusion parses them slightly abnormally.

Test Plan: Clicked/dragged lines to select them. Observed URI. Reloaded page, got the right selection.

Reviewers: mydeveloperday

Reviewed By: mydeveloperday

Maniphest Tasks: T13105

Differential Revision: https://secure.phabricator.com/D19305