Merge pull request #22 from ashleyholt/master

Added info on NGA Gazetteer Data
Merge pull request #28 from ashleyholt/master

Added OSUK POI Example
Merge pull request #29 from ashleyholt/master

Added Google POI example
simplified model
Merge branch 'master' of https://github.com/opengis/poi
new spec using OGC HTML template
cleaning up asciidoc
clean up
Changed link to poi-core.html