Add readme with install instructions

README.md

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+# Acamar
+Acamar is an open source service for pinging Minecraft servers and write results into MySQL backend.
+It supports all Minecraft versions from 1.5 to 1.11 and probably future versions.
+
+## Prerequisites
+- Java 8 or newer
+- Running MySQL or another compatible database (MariaDB, Amazon Aurora)
+
+## Installation
+1. Grab the latest version from the releases
+2. Run `java -Xmx128M -jar acamar-VERSION.jar`
+3. Edit `config.json` file
+4. Restart application
+
+## Configuration
+```D
+{
+  "pollDelay": 3000, // Delay between pings in milliseconds
+  "timeout": 2000, // If the server does not respond after this time, then it will be considered offline
+  "threads": 3, // Maximum amount of concurrent ping requests
+  "mysql": {
+    "url": "jdbc:mysql://127.0.0.1/database?useUnicode=true&characterEncoding=utf-8", // JDBC URL
+    "user": "root", // Username for database
+    "pass": "", // Password for database
+    // Next query will be executed every time when server is online
+    "onlineQuery": "UPDATE servers SET updated = {time}, online = {online}, max = {max} WHERE id = {id}",
+    // Offline query will be executed every time when server is offline
+    "offlineQuery": "UPDATE servers SET updated = 1 WHERE id = {id}",
+    // Query will be executed only once, when nothing is updated with any of previous queries
+    "insertQuery": "INSERT IGNORE INTO servers (id) VALUES ({id})"
+  },
+  "servers": {
+    "hypixel": { // Server ID
+      "host": "mc.hypixel.net", // Server hostname or IP
+      "port": 25565, // Server port
+      "version": "1.9" // Server version (1.6, 1.7, 1.8, 1.9, 1.10 and so on)
+    },
+    "vimeworld": { // One more server
+      "host": "vimeworld.net",
+      "port": 25565,
+      "version": "1.6"
+    }
+  }
+}
+```
+In MySQL queries you can insert some data from ping result:
+- `{id}` - Server ID from config
+- `{motd}` - Server's Message of the day (description in servers list)
+- `{online}` - Amount of players online
+- `{max}` - Maximum amount of players
+- `{time}` - Current unix timestamp in seconds
+
+If you don't have suitable table in your database, you can create one:
+```SQL
+CREATE TABLE `servers` (
+  `id` varchar(30) NOT NULL DEFAULT '',
+  `updated` int(11) DEFAULT '0',
+  `max` int(11) DEFAULT '0',
+  `online` int(11) DEFAULT '0',
+  `motd` varchar(255) DEFAULT NULL,
+  PRIMARY KEY (`id`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+```