[log] IDEA-115675 IDEA-116040 Fix table columns sizing

* Set sizes of table columns once, after the actual TableModel with
  commits is applied to the table. Don't set sizes again afterwards.
* Don't hardcode sizes:
  - let commit column occupy as much as possible;
  - let author column be as wide as the longest person name among the
    recent commits;
  - let the date be as wide as needed (no need to calculate,
    because dates are always nearly the same).

Implemented with the great help of Vassiliy Kudryashov.
[log] fix name of variable