Add sql definition for Submissions.

highscores_database.sql

@@ -42,4 +42,14 @@ CREATE TABLE Scores(
    CategoryId int unsigned not null,
    FOREIGN KEY (CategoryId) REFERENCES Categories(CategoryId) ON DELETE CASCADE,
    PRIMARY KEY (CategoryId, UserName)
+);
+
+CREATE TABLE Submissions(
+   CategoryId int unsigned not null,
+   GroupId int unsigned not null,
+   Score float not null,
+   SubmissionMessageId bigint unsigned not null,
+   UserName varchar(30) not null,
+   VerificationMessageId bigint unsigned not null,
+   PRIMARY KEY (CategoryId, GroupId, UserName)
 );