Improve error handling for invalid setup for directory permissions

When I started the server, I got this error:
ERROR You need root privileges to start on this port

It doesn't make sense because I wasn't running on port 80. So debugging it more (added console statements), I found that the true error was the following:

{ Error: EACCES: permission denied, mkdir '/var/www/solid.mysite/config/templates'
    at Object.fs.mkdirSync (fs.js:885:18)
    at mkdirsSync (/usr/lib/node_modules/solid-server/node_modules/fs-extra/lib/mkdirs/mkdirs-sync.js:31:9)
    at Object.mkdirsSync (/usr/lib/node_modules/solid-server/node_modules/fs-extra/lib/mkdirs/mkdirs-sync.js:37:16)
    at Object.copySync (/usr/lib/node_modules/solid-server/node_modules/fs-extra/lib/copy-sync/copy-sync.js:49:37)
    at ensureDirCopyExists (/usr/lib/node_modules/solid-server/lib/server-config.js:25:8)
    at Object.initTemplateDirs (/usr/lib/node_modules/solid-server/lib/server-config.js:108:29)
    at createApp (/usr/lib/node_modules/solid-server/lib/create-app.js:45:27)
    at Function.createServer (/usr/lib/node_modules/solid-server/lib/create-server.js:15:18)
    at bin (/usr/lib/node_modules/solid-server/bin/lib/start.js:122:17)
    at fs.readFile (/usr/lib/node_modules/solid-server/bin/lib/start.js:41:7)
  errno: -13,
  code: 'EACCES',
  syscall: 'mkdir',
  path: '/var/www/solid.mysite/config/templates' }

It should assist the user to fix their permissions not run it in root.

Start in bin/lib/start.js, then follow the startup path through lib/create-server.js, lib/create-app.js, and lib/server-config.js, especially the template-directory initialization. Reproduce startup with a directory that cannot be created and inspect how the EACCES failure is reported. Done means the permission error is surfaced accurately instead of being reported as a root-privilege or port error.