Add promise to ghost startup process to allow
hooking into when ghost has finished loading

addresses item 9 in #2078
and makes progress on #2182

- has files that startup ghost return a promise
 that is resolved once ghost has finished loading
- moves getSocket into config file
- removes models.reset() as it's not used anywhere
- update functions in server startup
- remove unused version hash variable
Merge pull request #2225 from hswolff/ghost-startup

Add promise to ghost startup process to allow