splitClusters uses Grapheme Cluster Boundary rules

unicodejs.graphemebreak.js
* New file: singleton class with splitClusters method
* On load, builds graphemeBreakRegexp from unicodejs.graphemebreakproperties.js

unicodejs.js
* Remove old splitClusters method (was just a placeholder)
* Change "conjunction" -> "disjunction", for consistency and correctness

unicodejs.textstring.js
* Use new splitClusters method

modules/ve/ve.js
* Use new splitClusters method

unicodejs.wordbreak.text.js
* Add new splitClusters test
* Refactor charRangeArrayRegexp test to use splitClusters

PHP files
* add unicodejs.graphemebreak.js, unicodejs.graphemebreakproperties.js

.docs/categories.json
* add unicodeJS.wordbreak class

Change-Id: I8f512e2fc2c46eb4b5f00994a8dac88f3c8f7dd2
Merge "splitClusters uses Grapheme Cluster Boundary rules"