docs(server): documentation about server configuration

docs/SERVER.md

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+## Data directory configuration
+
+File package.json contains path to data directory, you can move this folder to any other (by default data directory for web server same as root folder with package.json). 
+
+```json
+{
+	...
+	"serverDataDirectory": "./",
+	...
+}
+```
+
+This directory always contain logs and other configuration entities.
+
+## Configuration
+
+After server start in root folder will created rats.json - main configuration files. You can configurate port and database path in it:
+
+```json
+{
+    "dbPath": "e:\\Projects\\rats\\db",
+    "peerId": "qpxh1prxtvdp149dhw0nu",
+    "httpPort": 8095
+} 
+```
+
+Where "httpPort" port which listen http server and "dbPath" path to database folder with collection of torrents