初始化项目提交，并添加 flowable 7 的 dm 兼容

sql/db2/README.md

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+暂未适配 IBM DB2 数据库，如果你有需要，可以微信联系 wangwenbin-server 一起建设。
+
+你需要把表结构与数据导入到 DM 数据库，我来测试与适配代码。

sql/dm/flowable-patch/src/main/resources/META-INF/package-info.md

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+防止IDEA将`.`和`/`混为一谈

sql/dm/flowable-patch/src/main/resources/META-INF/services/liquibase.database.Database

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+liquibase.database.core.CockroachDatabase
+liquibase.database.core.DB2Database
+liquibase.database.core.Db2zDatabase
+liquibase.database.core.DerbyDatabase
+liquibase.database.core.Firebird3Database
+liquibase.database.core.FirebirdDatabase
+liquibase.database.core.H2Database
+liquibase.database.core.HsqlDatabase
+liquibase.database.core.InformixDatabase
+liquibase.database.core.Ingres9Database
+liquibase.database.core.MSSQLDatabase
+liquibase.database.core.MariaDBDatabase
+liquibase.database.core.MockDatabase
+liquibase.database.core.MySQLDatabase
+liquibase.database.core.OracleDatabase
+liquibase.database.core.PostgresDatabase
+liquibase.database.core.SQLiteDatabase
+liquibase.database.core.SybaseASADatabase
+liquibase.database.core.SybaseDatabase
+liquibase.database.core.DmDatabase
+liquibase.database.core.UnsupportedDatabase