redesign string parsers

alib2algo/test-src/regexp/RegExpTest.cpp

alib2algo/test-src/regexp/properties/RegExpEmptyTest.cpp

alib2algo/test-src/regexp/properties/RegExpEpsilonTest.cpp

alib2algo/test-src/regexp/simplify/RegExpOptimizeTest.cpp

alib2algo/test-src/regexp/toAutomaton/re2faTest.cpp

...2algo/test-src/regexp/transform/RegExpConcatenateTest.cpp

alib2algo/test-src/regexp/transform/RegExpDerivationTest.cpp

alib2algo/test-src/regexp/transform/RegExpIntegralTest.cpp

alib2aux/src/convert/DotConverter.h

alib2aux/src/convert/GasTexConverter.h

alib2aux/src/convert/TikZConverter.h

alib2str/src/StringApi.hpp

alib2str/src/abstraction/StringReaderAbstraction.hpp

alib2str/src/abstraction/StringReaderRegistry.cpp

alib2str/src/abstraction/StringReaderRegistry.hpp

alib2str/src/abstraction/StringWriterAbstraction.hpp

alib2str/src/abstraction/StringWriterRegistry.cpp

alib2str/src/abstraction/StringWriterRegistry.hpp

alib2str/src/alphabet/string/BarSymbol.cpp

alib2str/src/alphabet/string/BarSymbol.h