#173 Installation: custom config paths

[Adam Franco]

Would be good to be able to specify a custom config directory as well as custom directories for themes, templates, plugins, and text-templates without having to make modifications within the Segue source directory.

Doing this would allow segue upgrades to just involve replacing the source directory rather than requiring the additional steps of copying/linking in all of the custom configs, themes, etc.

One possible implementation would be to have segue look for a SEGUE_LOCAL_DIRS file in the parent of the source root that could contain a configuration of the paths to use for local/custom configuration, themes, etc.