Issue #250
Merge pull request #251 from Bohdan-Tereta/test

Issue #250 fixed
Merge pull request #252 from AnnaStorozhenko/development

To issue #145 dismissed employees are removed from statistic by positions
Merge pull request #256 from EricpolUkraine/test

Release merge from 'test' to 'development' (v1.13.1)
Merge pull request #257 from EricpolUkraine/master

Release merge from 'master' to 'development' (v1.13.1)
ExcelLirary.dll modified, worksheet renamed to 'BusinessTripsByUnits', unit tests updated