Derive MT subsentence map from uppercasing

See https://www.mediawiki.org/wiki/Content_translation/Markup

bin/apertium-xhtml
* Executable script for testing

mt/Apertium.js
* Subsentence map detection logic

lineardoc/LinearDoc.js
* Tag range info functionality

tests/*
* Unit tests for subsentence mapping

Change-Id: I6d1483e69aae979a684728f7724f6874194eee11
Merge "Derive MT subsentence map from uppercasing"