Merge branch 'sourceDeps_build' into 'master'

Source deps build

See merge request fdroid/fdroidclient!599

extern/nanohttpd/core/build.gradle

@@ -2,6 +2,9 @@ apply plugin: 'java'
 
 version = '2.1.0'
 
+sourceCompatibility = 1.7
+targetCompatibility = 1.7
+
 jar {
     baseName = 'nanohttpd'
 }

extern/support-v4-preferencefragment/build.gradle

@@ -1,6 +1,6 @@
 buildscript {
     repositories {
-        mavenCentral()
+        jcenter()
     }
 
     dependencies {

extern/zipsigner/build.gradle

@@ -4,6 +4,9 @@ repositories {
     jcenter()
 }
 
+sourceCompatibility = 1.7
+targetCompatibility = 1.7
+
 dependencies {
     compile 'com.madgag.spongycastle:pkix:1.53.0.0'
     compile 'com.madgag.spongycastle:prov:1.53.0.0'