add soci::binary support for CLOB/BINARY columns

following features are included:

  - transparent support of binary data for simple var in/out
  - transparent support of binary data for vector based in/out
  - transparent support of binary data for row (dt_binary type)
  - new connection options for CLOB/BINARY limits
  - superset capabilities for binary longer than connection limits
  - full support based on subclassed std::vector<unsigned char>