Fix for incompatible method call regarding IDEA <2018.2.

Heavy refactoring regarding quick fixes (using more extensions).
Even more refactoring.
Fixed/extended AssertThatGuavaOptionalInspection regarding static.
imports and wrong reference to core assertThat() where Guava assertThat() actually was necessary.

build.gradle

@@ -5,7 +5,7 @@ plugins {
 }
 
 group 'de.platon42'
-version '0.4'
+version '0.5'
 
 repositories {
     mavenCentral()
@@ -41,6 +41,11 @@ intellij {
 
 patchPluginXml {
     changeNotes """
+  <h4>V0.5 (13-Apr-19)</h4>
+    <ul>
+      <li>Fixed incompatibility with IDEA versions < 2018.2 (affected AssertThatSizeInspection).
+      <li>Fixed missing Guava imports (if not already present) for AssertThatGuavaInspection. This was a major PITA to get right.
+    </ul>
   <h4>V0.4 (11-Apr-19)</h4>
     <ul>
       <li>Reduced minimal supported IDEA version from 2018.2 to 2017.2.