Define tabulation width in term of spaces instead of pixels

[rlaverde]

In PR #3663 I assume that tabulation width will be always 4 spaces, and indentation could look wrong depending of tab_stop_width value, I think this could be improved defining it in spaces instead of pixels

I suggest:

• change:
  /config/main.py
  'tab_stop_width': 40,
  to
  'tab_stop_width_spaces': 4,

• use tab_stop_width_spaces in fix_indent calculations

• and set tab stop using space width
  self.setTabStopWidth('tab_stop_width_spaces * self.editor.fontMetrics().width(' '))

[ccordoba12]

Please don't forget to reference the issues you open from your PRs :-)

[rlaverde]

@ccordoba12 It's ok to do this change? any suggestions? I'll work on it

[ccordoba12]

Yeah, please go for it! I haven't touched our support for tabs in a long time, so it'd be really nice to improve it (given that we already offer it :-)