Database dialects, proper database shutdown, pagination in configuration.

Added possibility to use different database (storage) backends. Currently
supported: flatfiles and mysql. Fixes #2.

Added database shutdown call. This call will properly shutdown database
connections (in case of RDBMS) or flush pastes index cache on disk (in
case of flatfiles).

De-hardcoded pagination count. Fixes #12.

database/dialects/interface/dialectinterface.go

@@ -0,0 +1,43 @@
+// Fast Paste Bin - uberfast and easy-to-use pastebin.
+//
+// Copyright (c) 2018, Stanislav N. aka pztrn and Fast Paste Bin
+// developers.
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject
+// to the following conditions:
+//
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
+// OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+package dialectinterface
+
+import (
+	// stdlib
+	"database/sql"
+
+	// local
+	"github.com/pztrn/fastpastebin/pastes/model"
+)
+
+type Interface interface {
+	GetDatabaseConnection() *sql.DB
+	GetPaste(pasteID int) (*pastesmodel.Paste, error)
+	GetPagedPastes(page int) ([]pastesmodel.Paste, error)
+	GetPastesPages() int
+	Initialize()
+	SavePaste(p *pastesmodel.Paste) (int64, error)
+	Shutdown()
+}