WIP: SELECT for GRPC API

include/CMakeLists.txt

include/caosdb/result_set.h

include/caosdb/result_table.h

include/caosdb/transaction.h

include/caosdb/value.h

src/CMakeLists.txt

src/caosdb/result_set.cpp

src/caosdb/result_table.cpp

src/caosdb/transaction.cpp

test/test_issues.cpp

test/test_transaction.cpp