DatabaseCampaign: abstract campain for interaction with MySQL Database

The DatabaseCampaign interacts with the MySQL tables that are created
by the import-trace and prune-trace tools. It does offer all
unfinished experiment pilots from the database to the
fail-clients. Those clients send back a (by the experiment) defined
protobuf message as a result. The custom protobuf message does have to
need the form:

   import "DatabaseCampaignMessage.proto";

   message ExperimentMsg {
       required DatabaseCampaignMessage fsppilot = 1;

       repeated group Result = 2 {
          // custom fields
          required int32 bitoffset = 1;
          optional int32 result = 2;
       }
   }

The DatabaseCampaignMessage is the pilot identifier from the
database. For each of the repeated result entries a row in a table is
allocated. The structure of this table is constructed (by protobuf
reflection) from the description of the message. Each field in the
Result group becomes a column in the result table. For the given
example it would be:

    CREATE TABLE result_ExperimentMessage(
           pilot_id INT,
           bitoffset INT NOT NULL,
           result INT,
           PRIMARY_KEY(pilot_id)
    )

Change-Id: I28fb5488e739d4098b823b42426c5760331027f8

src/core/comm/DatabaseCampaignMessage.proto

@@ -0,0 +1,13 @@
+import "google/protobuf/descriptor.proto";
+extend google.protobuf.FieldOptions {
+    optional bool sql_primary_key = 32382 [ default = false];
+    optional bool sql_ignore      = 32383 [ default = false];
+}
+
+message DatabaseCampaignMessage {
+    required int32 pilot_id      = 1 [(sql_primary_key) = true];
+    required int32 variant_id    = 2 [(sql_ignore) = true];
+    required int32 fspmethod_id  = 3 [(sql_ignore) = true];
+    required int32 instr2        = 4 [(sql_ignore) = true];
+    required int32 data_address  = 5 [(sql_ignore) = true];
+}