While we might never be able to have 100% of our code strict, we can at
the very least do it for all of our tests. This ensures that our tests
are using our API with the types as intended by the test author, and not
silently be cast to what our API requires.
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