Allow wrapper configuration file to be read from rails config dir

[mark-dce]

@cbeer would you be open to a change like this to let the wrapper config be read from a .yml config file in the rails application's config directory if such a config file exists?

Order of precedence (highest to lowest):

• command line parameters
• ./config/fcrepo_wrapper.yml (assumes you're launching from your application root, ignored)
• .fcrepo_wrapper (hidden file in the root of whatever project you're working on)
• ~/.fcrepo_wrapper (hidden file in the logged-in user's home directory)

[atz]

A symmetric change should be made in solr_wrapper, too, assuming this gets in.