Deprecate insufficiently traded assets

 - Remove assets from META-INF/services/bisq.asset.Asset
 - Preserve asset types but mark as @deprecated
 - @ignore asset tests

Preserving the types is important from a compatibility perspective.
Users who have traded these assets in the past, however few there may
be, need to be able to classload the asset type(s) in order to avoid
errors when browsing through their trade portfolio history.

assets/src/main/java/bisq/asset/coins/Koto.java

@@ -26,6 +26,10 @@
 
 import java.util.Arrays;
 
+/**
+ * @deprecated for insufficent trading
+ */
+@Deprecated(since = "0.9.0")
 public class Koto extends Coin {
 
     public Koto() {

assets/src/main/java/bisq/asset/coins/Obsidian.java

@@ -21,6 +21,10 @@
 import bisq.asset.Coin;
 import bisq.asset.NetworkParametersAdapter;
 
+/**
+ * @deprecated for insufficent trading
+ */
+@Deprecated(since = "0.9.0")
 public class Obsidian extends Coin {
 
     public Obsidian() {

assets/src/main/resources/META-INF/services/bisq.asset.Asset

@@ -63,7 +63,6 @@ bisq.asset.coins.InfinityEconomics
 bisq.asset.coins.Instacash
 bisq.asset.coins.InternetOfPeople
 bisq.asset.coins.Kekcoin
-bisq.asset.coins.Koto
 bisq.asset.coins.Kumacoin
 bisq.asset.coins.LBRY
 bisq.asset.coins.Lisk
@@ -95,7 +94,6 @@ bisq.asset.coins.Nilu
 bisq.asset.coins.Nimiq
 bisq.asset.coins.NuBits
 bisq.asset.coins.Nxt
-bisq.asset.coins.Obsidian
 bisq.asset.coins.Octocoin
 bisq.asset.coins.Particl
 bisq.asset.coins.PepeCash

assets/src/test/java/bisq/asset/coins/KotoTest.java

@@ -19,8 +19,11 @@
 
 import bisq.asset.AbstractAssetTest;
 
+import org.junit.Ignore;
 import org.junit.Test;
 
+@Ignore
+@Deprecated
 public class KotoTest extends AbstractAssetTest {
 
     public KotoTest() {

assets/src/test/java/bisq/asset/coins/ObsidianTest.java

@@ -19,8 +19,11 @@
 
 import bisq.asset.AbstractAssetTest;
 
+import org.junit.Ignore;
 import org.junit.Test;
 
+@Ignore
+@Deprecated
 public class ObsidianTest extends AbstractAssetTest {
 
     public ObsidianTest() {