New @-codes: FILE_FTP_PATH and FILE_WEB_PATH (don't include scheme and host)

These @-codes can be used to construct ftp[s] and http[s] URLs to display to
users. For use in new/optional display file text/menu/download.*

Add optional configurable 'vpath' (per-directory) for directories that have
web/ftp aliases, so they preferred/short path (alias) will be used in the
expanded @-codes.

In SCFG, display each directory's virtual file path ([auto-generated] or set
manually).

getfilevpath() no longer assumes the target buf is >= MAX_PATH+1 bytes long

Add dir_vpath() to get a directory's vpath

Extend maximum file library parent directory from 47 to 100 chars. This limit
was likely imposed because we didn't have horiztonal scrolling input in UIFC
getstr() support at the time. We're no longer limited by that.