closes#5358
- Moved node version check and exits if not supported
- Removed upgrade warning from `ghost-server.js`
- Perform a check for NODE_ENV, uses `config.example.js` if none apparent
Refs #3864
- Make sure that require() is able to resolve all dependencies
listed in package.json. If packages are missing halt the
bootstrap process and display an error and help message for user.
- Check that contentPath and its subdirectories exist with the correct
permissions.
- Check sqlite3 database file is set for read/write access.
