[tmux/en] Improve style & content

 Style changes
  - Site format has changed back to ~80 columns, certain rows have had line breaks removed.
  - Indentation has been adjusted globally to give additional space and consistency.
  - 'Configuring Tmux' has been separated from the preceding content due to long lines causing the entire page to scroll horizontally and block text.
  - tmux.conf has been reorganized to better explain settings categorically to new users.

 Content Changes
  - Unmapping the prefix key contained erroneous data
  - Misc section and it's contained "bind r source.." setting are superfluous, as when this points to the next file to use in the configuration, not the current file. Since no additional configuration files have been used, it has been removed.