Usability improvements: key bindings

1- there should be two clear sets of key bindings: one when the focus is in the calendar browser (left column) and one when the focus is in the event list (right column)
2- if an action cause the focus to change, it should be easily reverted: at this time, if I press the left arrow when in the event list, the focus is set to the calendar browser. The right arrow cannot bring me back to the event list and perform a totally different action (move to another day).

Suggestions:

• Create two distinct subsections in [keybindings]
• Use only tab (or another key) to switch between calendar/event list.
• Allow esc to return to calendar (as with vi). Prohibit left and right arrows in event list.

[keybindings]
  [[calendar]]
  focuseventlist: tab
  new: ...
  mark: ...
  # no `view` nor `duplicate` allowed in this subsection

  [[eventlist]]
  focuscalendar: tab, esc
  save: ...
  new: ...
  # no `left` nor `right` allowed in this subsection

Start by locating the keybindings configuration and the calendar-browser/event-list focus-handling entry points; the issue names no files or tests. Compare the current left/right, Tab, and Esc behavior with the proposed separate calendar and event-list bindings, then define completion as consistent focus switching and documented prohibited bindings.