Selectively disable some Gradle linter rules

Specifically, we're not really in a position now to deal with
duplicated classes among our dependencies.  Maybe we can try harder to
examine those in the future, but for now they are a distraction from
other issues that we can attack more readily.

build.gradle

@@ -74,7 +74,13 @@ buildscript {
 allprojects {
 	apply plugin: 'nebula.lint'
 	gradleLint.alwaysRun = false
-	gradleLint.rules = ['all-dependency']
+	gradleLint {
+		rules = ['all-dependency']
+		excludedRules = [
+			'duplicate-dependency-class',
+			'transitive-duplicate-dependency-class',
+			]
+	}
 }