When extracting sheet title from string reference (like `"Work!sheet1!A1"`), PHP function `explode()` divide this string into three parts: `['Work', 'sheet1', 'A1']`. And then these wrong values are used in formulas, ranges, etc.
This change fix that problem by using special function `Worksheet::extractSheetTitle()`. This function also has been changed to make sure that worksheet title can contain "!" character. So, that function search last position of "!" in reference string and divide it to 2 parts correctly: `['Work!sheet1', 'A1']`.
Fixes#325Fixes#662
Fixes a bug when calling `$sheet->freezePane('B2')` without a second argument.
The selected cell will now be `B2` instead of the incorrect `B3`.
Fixes#389Closes#393
Timur