add comment for flac-tools link, add links for archive.org, move "communities" section between "hardware" and "software" section

revamp ogg flac file decoder; it needed to be derived from the ogg flac stream encoder instead of the flac file encoder

fix up reporting of the current frame to the write callback; also fixes a problem with progress callbacks in the ogg flac file encoder

add undocumented option --apply-replaygain-which-is-not-lossless to flac; required a lot of reorganization; gain_analysis lib renamed to replaygain_analyis; replaygain_synthesis moved out of plugin_common into its own library in share/