Migrate to Xorm (#474)

close #234

* Migrate store
* Migrate tests
* Rewrite migrations
* Init fresh DB in on step
* Rm old stuff (meddler, sql files, dead code, ...)

server/store/common.go

@@ -0,0 +1,21 @@
+// Copyright 2021 Woodpecker Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package store
+
+// Opts are options for a new database connection
+type Opts struct {
+	Driver string
+	Config string
+}