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/shared-mutable-state-and-concurrency.md b/docs/shared-mutable-state-and-concurrency.md
index 8591f17..26005ee 100644
--- a/docs/shared-mutable-state-and-concurrency.md
+++ b/docs/shared-mutable-state-and-concurrency.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/SharedStateGuideTest.kt
+<!--- KNIT     ../kotlinx-coroutines-core/jvm/test/guide/.*\.kt -->
+<!--- TEST_OUT ../kotlinx-coroutines-core/jvm/test/guide/test/SharedStateGuideTest.kt
 // This file was automatically generated from coroutines-guide.md by Knit tool. Do not edit.
 package kotlinx.coroutines.guide.test
 
@@ -101,7 +101,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-sync-01.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-sync-01.kt)
 
 <!--- TEST LINES_START
 Completed 100000 actions in
@@ -152,7 +152,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-sync-01b.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-sync-01b.kt)
 
 <!--- TEST LINES_START
 Completed 100000 actions in
@@ -198,7 +198,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-sync-02.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-sync-02.kt)
 
 <!--- TEST LINES_START
 Completed 100000 actions in
@@ -253,7 +253,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-sync-03.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-sync-03.kt)
 
 <!--- TEST ARBITRARY_TIME
 Completed 100000 actions in xxx ms
@@ -310,7 +310,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-sync-04.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-sync-04.kt)
 
 <!--- TEST ARBITRARY_TIME
 Completed 100000 actions in xxx ms
@@ -364,7 +364,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-sync-05.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-sync-05.kt)
 
 <!--- TEST ARBITRARY_TIME
 Completed 100000 actions in xxx ms
@@ -423,7 +423,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-sync-06.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-sync-06.kt)
 
 <!--- TEST ARBITRARY_TIME
 Completed 100000 actions in xxx ms
@@ -539,7 +539,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-sync-07.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-sync-07.kt)
 
 <!--- TEST ARBITRARY_TIME
 Completed 100000 actions in xxx ms