Get rid of some warnings

build.gradle

@@ -17,12 +17,11 @@ repositories {
 
 dependencies {
     compile 'org.apache.jackrabbit:jackrabbit-webdav:2.12.4'
-    compile 'com.squareup.okhttp3:okhttp:3.10.0'
+    implementation 'com.squareup.okhttp3:okhttp:3.10.0'
 }
 
 android {
     compileSdkVersion 26
-    buildToolsVersion '26.0.2'
 
     sourceSets {
         main {

sample_client/build.gradle

@@ -5,12 +5,11 @@ repositories {
 }
 
 dependencies {
-    compile project(':')
+    implementation project(':')
 }
 
 android {
     compileSdkVersion 26
-    buildToolsVersion "26.0.2"
 
     sourceSets {
         main {

test_client/build.gradle

@@ -6,13 +6,12 @@ repositories {
 }
 
 dependencies {
-    compile 'commons-httpclient:commons-httpclient:3.1'
-    compile project(':')
+    implementation 'commons-httpclient:commons-httpclient:3.1'
+    implementation project(':')
 }
 
 android {
     compileSdkVersion 26
-    buildToolsVersion "26.0.2"
 
     sourceSets {
         main {

test_client/tests/build.gradle

@@ -1,13 +1,12 @@
 apply plugin: 'com.android.application'
 
 dependencies {
-    compile fileTree(dir: 'libs', include: '*.jar')
-    compile project(':')
+    implementation fileTree(dir: 'libs', include: '*.jar')
+    implementation project(':')
 }
 
 android {
     compileSdkVersion 26
-    buildToolsVersion "26.0.2"
 
     sourceSets {
         main {