Adjustments
- Change format of R_args to List (required to run R as Neovim job).

- Never call UpdateOB(); it will always be called by nvimcom. This is
  the most logical procedure, but wasn't adopted before because it
  causes problems for Vim.

- Move from nvimbuffer.vim to common_global.vim some code that was not
  used exclusively to run R as Neovim job.

- Rename SendToVimCom as SendToNvimcom and no longer user a variable
  pointing to the correct function since now there is only one function
  to send messages do nvimcom. Remove the no longer used second argument
  of SendToNvimcom ("I", to ignore reply).