Complete instantiations for eq::admin::Config::find<>
Connect to local server from admin client if possible
Fix async texture readback

Use PBO readback when available, texture otherwise to support Mesa OGL 1.4
Allow set of entire window settings; can be useful to transfer settings in the admin side
Fix semantics of Config::update()

- correct return value on failing resources
- cleanup fabric::Error
  - move error enums to separate file
  - encode originator in the error
  - serialize error as an object
- use return value for configInitFBO