Migration to new multiplatorm plugin (#947)

Migration to a new multiplatform plugin
  
  * kotlinx-coroutines-core-[common|js|native] are merged into one core module with multiple source sets
  * Folder structure and readme are restructured
  * Publication process is patched to preserve backward compatibility with artifact names
diff --git a/docs/select-expression.md b/docs/select-expression.md
index cf39b7b..f8604a1 100644
--- a/docs/select-expression.md
+++ b/docs/select-expression.md
@@ -6,8 +6,8 @@
 // This file was automatically generated from coroutines-guide.md by Knit tool. Do not edit.
 package kotlinx.coroutines.guide.$$1$$2
 -->
-<!--- KNIT     ../core/kotlinx-coroutines-core/test/guide/.*\.kt -->
-<!--- TEST_OUT ../core/kotlinx-coroutines-core/test/guide/test/SelectGuideTest.kt
+<!--- KNIT     ../kotlinx-coroutines-core/jvm/test/guide/.*\.kt -->
+<!--- TEST_OUT ../kotlinx-coroutines-core/jvm/test/guide/test/SelectGuideTest.kt
 // This file was automatically generated from coroutines-guide.md by Knit tool. Do not edit.
 package kotlinx.coroutines.guide.test
 
@@ -144,7 +144,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-select-01.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-select-01.kt)
 
 The result of this code is: 
 
@@ -235,7 +235,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-select-02.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-select-02.kt)
 
 The result of this code is quite interesting, so we'll analyze it in mode detail:
 
@@ -325,7 +325,7 @@
 
 </div> 
  
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-select-03.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-select-03.kt)
   
 So let us see what happens:
  
@@ -418,7 +418,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-select-04.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-select-04.kt)
 
 The output is:
 
@@ -537,7 +537,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-select-05.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-select-05.kt)
 
 The result of this code: