* [ts][summary.py] Extend `-o` to support tabs separated output.
* [ts][summary.py] Improve TABS sepatated output.
There is no need to print TAB at the beginning and at the end of each
row in the table.
Cosmetic change: using python list comprehension instead of for loop
to process a single row.
__ridx__ is an _undefined name_ in this context but __self.ridx__ is used three other times in this method and nine times in this class. Undefined names may raise [NameError](https://docs.python.org/3/library/exceptions.html#NameError) at runtime.
flake8 testing of https://github.com/opencv/opencv
$ __flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics__
```
./modules/ts/misc/table_formatter.py:50:23: F821 undefined name 'ridx'
self.rows[ridx + 1].props = properties
^
```
Legend for new column is:
* FASTER - strong speedup
* faster - spedup is detected but it is unreliable
* <empty> - no change in speed
* slower - slowdown is detected but it is unreliable
* SLOWER - strong slowdown
