Update build config, gitignore after testing

OpenKeychain/build.gradle

@@ -268,10 +268,11 @@ android {
 
     dexOptions {
         incremental = true
-        // Disable preDexing, causes com.android.dx.cf.iface.ParseException: bad class file magic (cafebabe) or version (0034.0000) on some systems
-        preDexLibraries = false
+        preDexLibraries = true
+        // dexInProcess requires much RAM, which is not available on all dev systems
+        dexInProcess = false
         jumboMode = true
-        javaMaxHeapSize "2g"
+        javaMaxHeapSize "4g"
     }
 
     packagingOptions {
@@ -285,8 +286,6 @@ android {
     }
 }
 
-// apply plugin: 'spoon'
-
 task jacocoTestReport(type:JacocoReport, dependsOn: "testFdroidDebugUnitTest") {
     group = "Reporting"
     description = "Generate Jacoco coverage reports"