v3.1.0-fix

Changes:

• bug: delete $tpm_plugins_variable_name and using command,
  this show double output with _tmux_conf_contents function.
• bug: fix the clean_plugins function and delete too many slashes, TMUX_PLUGIN_MANAGER_PATH default is set to / at the path end.
• bug: in bindings\clean_plugins when using >/dev/null 2>&1 no output on screen. Fix delete the command.
• change location of verify_tpm_path_permissions function from scripts/install_plugins.sh to scripts/helper/utility.sh.
  Reason: it is a helper function, not a install function.
• bug: add missing shebang in some files.
• bug: in bindings\install_plugins when using >/dev/null 2>&1 no output on screen. Fix delete the command.
• bug: when using vi copy mode, Enter does not quit screen after tpm
  installation/update. Fix by making q the key for vi mode.

Full Changelog: https://github.com/slange-dev/tpm/blob/v3.1.0-fix/CHANGELOG.md