Improvement suggestion: allow well-known prefixes in hdtSearch

[AxelPolleres]

another proposal is to add an option, e.g. -p to hdtSearch to try to expand prefixes in patterns with well-known names automatically, the well known names could be included from http://prefix.cc/ (but I admittedly don't know how to dump the data from there, cause doing that with HTTP requests might be kinda annouying, though possible... will try to find out