Refactor CompilerConfiguration: keys -> Content roots

Represent classpath roots and java source roots as separate entities

compiler/frontend/src/org/jetbrains/kotlin/config/CommonConfigurationKeys.java

@@ -24,7 +24,8 @@ public class CommonConfigurationKeys {
     private CommonConfigurationKeys() {
     }
 
-    public static final CompilerConfigurationKey<List<String>> SOURCE_ROOTS_KEY = CompilerConfigurationKey.create("source roots");
+    // roots, including dependencies and own source
+    public static final CompilerConfigurationKey<List<ContentRoot>> CONTENT_ROOTS = CompilerConfigurationKey.create("content roots");
 
     public static final CompilerConfigurationKey<List<JetScriptDefinition>> SCRIPT_DEFINITIONS_KEY = CompilerConfigurationKey.create("script definitions");
 }

compiler/frontend/src/org/jetbrains/kotlin/config/ContentRoots.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2010-2015 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.config
+
+public trait ContentRoot
+
+public data class KotlinSourceRoot(public val path: String): ContentRoot
+
+public fun CompilerConfiguration.addKotlinSourceRoot(source: String) {
+    add(CommonConfigurationKeys.CONTENT_ROOTS, KotlinSourceRoot(source))
+}
+
+public fun CompilerConfiguration.addKotlinSourceRoots(sources: List<String>): Unit = sources.forEach { addKotlinSourceRoot(it) }
+