update gradle and some submodule build versions

extern/openpgp-api-lib

@@ -1 +1 @@
-Subproject commit 3d77d941868e81ac2a5d6317c24a3df6739e187a
+Subproject commit 72896baa40918830a66a24c2616fb3bcbb4bfddd

gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.0-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.4.1-all.zip

sshauthentication-api/build.gradle

@@ -7,7 +7,7 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.1.4'
+        classpath 'com.android.tools.build:gradle:3.5.3'
         classpath 'com.novoda:bintray-release:0.8.0'
     }
 }
@@ -16,18 +16,13 @@ android {
     if (project.hasProperty('rootProject.ext.compileSdkVersion')) {
         compileSdkVersion rootProject.ext.compileSdkVersion
     } else {
-        compileSdkVersion 27
-    }
-    if (project.hasProperty('rootProject.ext.buildToolsVersion')) {
-        buildToolsVersion rootProject.ext.buildToolsVersion
-    } else {
-        buildToolsVersion '27.0.3'
+        compileSdkVersion 28
     }
 
 
     defaultConfig {
-        minSdkVersion 9
-        targetSdkVersion 25
+        minSdkVersion 14
+        targetSdkVersion 28
         versionCode 1
         versionName "1.0"
     }