[validator]-revise string validator length message

[mononobi]

revise error message for string validator on invalid length to mention the required min or max length on error.
also add data key into options in api exception handlers.
also add support for callable min and max values in range and min and max validator.
also add a method to those validators to get representation of value to be used for complex types like datetime ....
also add lazy=True as default in validation services.
on lazy validation do not add data if only one item is available in list. also revise lazy validation message.

[mononobi]

all done.
only dynamic(callable) validators are left to be implemented.

[mononobi]

All done