introduces sql-parser
basic string parsing: remove whitespaces
adds new Statement class
introduces Statement::parse() and statement_ptr_t
parser now considers String input ("...")
adds keyword registration and select statement/keyword
moved select into subfolder
usufull main ...
[wip] adds ConstantStatement for constant expressions like numbers
deeper hierarchy and more constant expressions evauable
registration of kaywords in one file
better names
adds Operator Class for operators like + - =
adds more constant expressions (float, string, int, null)
adds empty class for LeqOperator (<=)
new unimplemented expressions, priority as abstract function and better string parsing