Gradle 5 support

[vehovsky]

The plugin fails when used with Gradle 5 with following exception:

Caused by: java.lang.NullPointerException: Gradle does not allow passing null for the configuration action for CopySpec.from(). at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:906) at org.gradle.api.internal.file.copy.DefaultCopySpec.from(DefaultCopySpec.java:132) at org.gradle.api.tasks.AbstractCopyTask.from(AbstractCopyTask.java:324) at org.gradle.api.tasks.AbstractCopyTask$from.callCurrent(Unknown Source) at us.kirchmeier.capsule.task.Capsule.applyDefaultCapsuleSet(Capsule.groovy:150) at us.kirchmeier.capsule.task.Capsule.finalizeSettings(Capsule.groovy:125) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:104) at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:326) at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:352) at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.callCurrent(PogoMetaClassSite.java:68) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:160) at us.kirchmeier.capsule.task.Capsule$_closure1.doCall(Capsule.groovy:63)