KT-18674 Join Lines should join strings (#1305)

* Join Lines should join strings #KT-18674 Fixed

* #KT-18674 Fixed

idea/testData/joinLines/stringTemplate/firstLineVariable.kt

@@ -0,0 +1,5 @@
+fun test() {
+    val foo = "1"
+    val s = foo +<caret>
+            "bar"
+}

idea/testData/joinLines/stringTemplate/firstLineVariable.kt.after

@@ -0,0 +1,4 @@
+fun test() {
+    val foo = "1"
+    val s = foo +<caret> "bar"
+}

idea/testData/joinLines/stringTemplate/secondLineVariable.kt

@@ -0,0 +1,5 @@
+fun test() {
+    val foo = "1"
+    val s = "bar" +<caret>
+            foo
+}

idea/testData/joinLines/stringTemplate/secondLineVariable.kt.after

@@ -0,0 +1,4 @@
+fun test() {
+    val foo = "1"
+    val s = "bar" +<caret> foo
+}

idea/testData/joinLines/stringTemplate/simple.kt

@@ -0,0 +1,4 @@
+fun test() {
+    val s = "foo" +<caret>
+            "bar"
+}

idea/testData/joinLines/stringTemplate/simple.kt.after

@@ -0,0 +1,3 @@
+fun test() {
+    val s = "foo<caret>bar"
+}

idea/testData/joinLines/stringTemplate/threeLines.kt

@@ -0,0 +1,5 @@
+fun test() {
+    val s = "foo" +<caret>
+            "bar" +
+            "baz"
+}

idea/testData/joinLines/stringTemplate/threeLines.kt.after

@@ -0,0 +1,4 @@
+fun test() {
+    val s = "foo<caret>bar" +
+            "baz"
+}