Add user options for links between main and notes files; simplify org-remark-global-tracking

[nobiot]

• chg: `org-remark-global-tracking-mode' has been simplified.

   .org-remark-tracking file is no longer necessary and can be safely
   deleted from the user's Emacs configuration directory if present.
   Automatic activation of `org-remark-mode' is done by looking the
   presence of a marginal notes file for current buffer open.
  
   `org-remark-global-tracking-mode' itself is still relevant and
   recommended to be setup as was previously in the user manual.
  
   This is not expected to break the user's workflow -- removing a superfluous feature.

• add: Option to use relative links from the marginal notes back to the source

   Adding user option org-remark-source-path-function.  The default is
   file-relative-name.

• add: Adding a new option to org-remark-notes-file-path to use a function

   Its default function is org-remark-notes-file-path-function.  It
   returns a file name like this: "FILE-notes.org" by adding
   "-notes.org" as a suffix to the file name without the extension.