1. 'TextCanOverlap' property was stored as false if TickLableSkip
      is not equal to one.
   2. For OOXML charts TickLableSkip can be between 1 to 999999999.
   3. We can not apply zero or less than zero  value to TickLableSkip.
      ( As per specification)
   4. In axis model default value for TickLableSkip was zero which is
      incorrect.
   5. Added unit test to check 'TextCanOverlap' property for chart.

Change-Id: Ib3104b1d932f6e9376c149eabb201c8e9ad23da9
Reviewed-on: https://gerrit.libreoffice.org/11901Reviewed-by: Kohei Yoshida <libreoffice@kohei.us>
Tested-by: Kohei Yoshida <libreoffice@kohei.us>