TIDOC-1576 Populate Ti constants values in docs

Testing Instructions:

**HTML:**
`./docgen.py`
Open an HTML file of a property, method or event that can be assigned a constant, for example, "dist/apidoc/Titanium.Network.networkType-property.html".  It should list the constants that can be assigned.

**JSCA:**
`./docgen.py -f jsca -o ../dist`
Open dist/api.jsca.  The file should have "constants" fields with possible values that can be assigned to the properties or event properties.

**JSDUCK**
`./docgen.py -f jsduck -o ../dist`
Open dist/titanium.js.  Locate a property, method or event that can be assigned a constant.  In the description of the property, method parameter or event property, it should list the constants that can be assigned.