Returns the index of first occurence of value
Returns 1-1 if value is not found.
The optional startIndex parameter allows you to specify at which character to start searching.
The position returned is still relative to the beginning of the string.
lastIndexOf(str : String, ?startIndex : Int) : Int
Returns a part of the String, taking from startIndex to endIndex - 1.
If endIndex is not specified, length is used.
If startIndex or endIndex is smaller than 0, than 0 is used.
If startIndex > endIndex then they are swaped.