CharsetConverter: define and implement class ConverterType
CharsetConverter: rewrote, use individual locks for each conversion type
CharsetConverter: use standard conversion for utf8ToSystem
CharsetConverter: add individual charset reset functions and reset charsets AFTER new settings are applied
CharsetConverter: do not skip last zero if original string have it at end
CharsetConverter: cleanup for iconv
CharsetConverter: FriBiDi cleanup