for reading preferences on Windows, try HKCU first, then fall back to HKLM. For writing, only write to HKCU

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 Removed outdated expr-help file in favor of new documentation.