first draft of saving the preferences, including the gui preset (still won't write to file for some reason)

*further improved naming convention for settings files (default.settings and user.settings), cosmetic improvements to the indexing prompt of the help browser dialog.

*updated file locations and made names more consistent across all folders (everything now uses pd-l2ok instead of pdl2ork). Placed user settings into ~/.pd-l2ork/ folder and renamed to simply settings, placed xapian search database for the browser inside the ~/.pd-l2ork folder.

*updated most of the audio API to the latest version (with the exception of ALSA and JACK which are partial until our improvements can be merged and/or new implementation of JACK thoroughly tested to ensure we like its default behavior)

forgot to add another change to make it in sync with 0.43+ branch where real-time is default behavior.

reverted 0.43 backport as its implementation seems unstable when trying to (re)connect to jack via audio properties. Fixed a bug where closing jack while having DAC on would hang pd.

backported audio driver support from 0.43 and the pd/extra folder with supporting fixes/merges where needed. Removed outdated expr-help file in favor of new documentation.