Wisps now use Wisp=true flag in the main database. The separate
.beads-wisp/ directory is no longer needed.
Removed:
- WispDirName constant
- FindWispDir()
- FindWispDatabasePath()
- NewWispStorage()
- EnsureWispGitignore()
- IsWispDatabase()
- All related tests
- .beads-wisp/ from .gitignore