Added -statistics CLI argument with required parameter <path>.
Statistics module counts how many namespaces/types/members are added/removed/total.
If <path> parameter just points to a folder the default filename "statistics.txt" is appended. If the path can't be resolved a warning message is printed ("mdoc: Unable to save statistics file: Could not find a part of the path 'Z:\'.")
Unit tests for new classes are added; "check-monodocer-fx-statistics-remove" integration test is added, 2 other tests check statistics result file as well.
Closes #100
