[TD-2598] feature: C# taosdemo, support query command.

tests/examples/C#/taosdemo/README.md

@@ -12,23 +12,25 @@ Usage: mono taosdemo.exe [OPTION...]
 
         --help                   Show usage.
 
-        -h                host, The host to connect to TDengine. Default is localhost.
-        -p                port, The TCP/IP port number to use for the connection. Default is 0.
-        -u                user, The user name to use when connecting to the server. Default is 'root'.
-        -P                password, The password to use when connecting to the server. Default is 'taosdata'.
-        -d                database, Destination database. Default is 'test'.
-        -a                replica, Set the replica parameters of the database, Default 1, min: 1, max: 5.
-        -m                table_prefix, Table prefix name. Default is 't'.
+        -h <hostname>            host, The host to connect to TDengine. Default is localhost.
+        -p <port>                port, The TCP/IP port number to use for the connection. Default is 0.
+        -u <username>            user, The user name to use when connecting to the server. Default is 'root'.
+        -P <password>            password, The password to use when connecting to the server. Default is 'taosdata'.
+        -d <dbname>              database, Destination database. Default is 'test'.
+        -a <replications>        replica, Set the replica parameters of the database, Default 1, min: 1, max: 5.
+        -m <table prefix>        table_prefix, Table prefix name. Default is 't'.
         -M                       stable, Use super table.
-        -s                stable_prefix, STable prefix name. Default is 'st'
-        -T                num_of_threads, The number of threads. Default is 10.
-        -r                num_of_records_per_req, The number of records per request. Default is 1000.
-        -t                num_of_tables, The number of tables. Default is 1.
-        -n                num_of_records_per_table, The number of records per table. Default is 1.
-        -c                config_directory, Configuration directory. Default is '/etc/taos/'.
+        -s <stable prefix>       stable_prefix, STable prefix name. Default is 'st'
+        -Q <DEFAULT | command>   query, Execute query command. set 'DEFAULT' means select * from each table
+        -T <number>              num_of_threads, The number of threads. Default is 10.
+        -r <number>              num_of_records_per_req, The number of records per request. Default is 1000.
+        -t <number>              num_of_tables, The number of tables. Default is 1.
+        -n <number>              num_of_records_per_table, The number of records per table. Default is 1.
+        -c <path>                config_directory, Configuration directory. Default is '/etc/taos/'.
         -x                       flag, Insert only flag.
         -O                       order, Insert mode--0: In order, 1: Out of order. Default is in order.
-        -R                rate, Out of order data's rate--if order=1 Default 10, min: 0, max: 50.
-        -D                Delete data methods 0: don't delete, 1: delete by table, 2: delete by stable, 3: delete by database.
+        -R <number>              rate, Out of order data's rate--if order=1 Default 10, min: 0, max: 50.
+        -D <number>              Delete data methods 0: don't delete, 1: delete by table, 2: delete by stable, 3: delete by database.
         -v                       Print verbose output
+        -g                       Print debug output
         -y                       Skip read key for continous test, default is not skip