Change the javascript definitions to gdn.meta.

- Change definitions variable to gdn.meta.
- Output a more minimal script tag with just a single json_encode().
- Add gdn.getMeta() and gdn.setMeta() in global.js.
Document Gdn_Controller->DefinitionList() and add a $wrap parameter.
Add the ability to specify an inline scrip with HeadModule->AddScript().
Add the definition list to the head module rather than the foot asset.
Merge pull request #2068 from vanilla/hotfix/definitions-to-meta

Client-side Definition Refactor