these should behave like the python str methods & functions/the DDR_Library lambdas, but be implemented in native C++ for higher efficiency

strJoin: doesnt ignore nil/empty
strSplit: provides empty strings where appropriate, splits by entire delimiter sequences, not individual delimiter characters. Can take list of delimiters instead? Also takes an optional parameter N, which is number of splits to make (starting from front). Also takes an optional parameter O, which is number of splits to skip over (offset).
strReplace: replace one sequence with another sequence inside of a given string
strCount: counts occurrences
strStrip: removes whitespaces from ends
strSlice: as subset, but returns empty strings instead of nils where appropriate, handles negative indexes (counting from back of string)
strContains: True if strB is in strA
strStartsWith: True if leading characters of strA are exactly strB
strEndsWith: True if ending characters of strA are exactly strB