Add seek command (supersedes #344) (#674)

* Add seek command

* Combine nested if statements

* Put the seek command in correct place to keep alphabetical order

* Add license header

* Brackets on next line

* Restructure if-statements

* Check for permissions with DJCommand#checkDJPermission

* Make regex slightly smaller

* Optimize imports

* Output length of current track if requested seek time is invalid

* Restate seeked point when seeked successfully

* Add empty newline at end of file to keep consistency

* Create TimeUtil class for parsing and formatting time

* Move FormatUtil#formatTime to TimeUtil, and refactor

* Apply requested changes (Pass 2)

* Seek based on current position in track

* Apply requested changes (Pass 3)

* Add javadoc param

* Apply requested changes (Pass 4)

* Fix merge

* Avoid reassigning parameter (Codacy)

* Rework timestamp parsing

* Refactor timestamp parsing

* Apply requested changes (Pass 5)

* Add examples in help

* Apply requested changes (Pass 6)

* Fix missing import

* Keep track of start timestamp & add "unit" times

* Fix my abdominal merge with QueuedTrack

* Use RequestMetadata to store start timestamp

* Store request info in request metadata

* Add regex to try getting a timestamp from the url

* Require RequestMetadata for QueuedTracks

* Add some unit tests for unit seeking

* Add docs & examples

---------

Co-authored-by: Whew., Inc <22574706+Whew-Inc@users.noreply.github.com>

src/main/java/com/jagrosh/jmusicbot/BotConfig.java

@@ -16,8 +16,8 @@
 package com.jagrosh.jmusicbot;
 
 import com.jagrosh.jmusicbot.entities.Prompt;
-import com.jagrosh.jmusicbot.utils.FormatUtil;
 import com.jagrosh.jmusicbot.utils.OtherUtil;
+import com.jagrosh.jmusicbot.utils.TimeUtil;
 import com.sedmelluq.discord.lavaplayer.track.AudioTrack;
 import com.typesafe.config.*;
 import java.io.IOException;
@@ -336,7 +336,7 @@ public class BotConfig
     
     public String getMaxTime()
     {
-        return FormatUtil.formatTime(maxSeconds * 1000);
+        return TimeUtil.formatTime(maxSeconds * 1000);
     }
 
     public long getAloneTimeUntilStop()