vim-helper for using vim for lots of tasks

Initially for looking up man pages.
disable Mac Terminal icon for tmux in xtermtitle
Made auto-tmux attach after all plugins load

- with heavy refactoring of command manipulations for PROMPT_COMMAND,
  CHPWD_COMMAND, ONEXIT_COMMAND.
Simplified bpm.* modules organization.

- bpm.utils         for common vocabularies.
- bpm.events        for handling events, e.g., prompt, chpwd, exit.
- bpm.interactive   for interactive helpers, e.g., getting a key.
tex-helper should first check latexmk availability
Suppressed noise related to tmux set-window-option
Fixed misuse of bash_add_unloader
Respecting forced xtermtitle_mac_terminal=true
atmux-{record,respawn}-windows

for at least restoring the tmux windows after reboots.
Workaround for broken tmux-cwd-title