completely remove not needed alphabet::Symbol class

...o_experimental/src/grammar/parsing/AbsorbTerminalSymbol.h

...lgo_experimental/src/grammar/parsing/CornerSubstitution.h

...rimental/src/grammar/parsing/DeterministicLL1ParseTable.h

...go_experimental/src/grammar/parsing/ExtractRightContext.h

...perimental/src/grammar/parsing/HandleFirstFirstConflict.h

...erimental/src/grammar/parsing/HandleFirstFollowConflict.h

alib2algo_experimental/src/grammar/parsing/LRParser.h

alib2algo_experimental/src/grammar/parsing/LeftFactorize.h

...algo_experimental/src/grammar/parsing/common/Substitute.h

alib2algo_experimental/test-src/grammar/parsing/LR0Parser.h

alib2algo_experimental/test-src/grammar/parsing/LRParser.h

...go_experimental/test-src/grammar/parsing/SLR1ParseTable.h

alib2data/src/alphabet/BarSymbol.h

alib2data/src/alphabet/BlankSymbol.h

alib2data/src/alphabet/BottomOfTheStackSymbol.h

alib2data/src/alphabet/EndSymbol.h

alib2data/src/alphabet/InitialSymbol.h

alib2data/src/alphabet/NonlinearVariableSymbol.h

alib2data/src/alphabet/StartSymbol.h

alib2data/src/alphabet/Symbol.h