enable optimisations and minifying for release builds

* closes #19
* update gradle wrapper to version 6.6

app/build.gradle

@@ -19,8 +19,8 @@ android {
 
     buildTypes {
         release {
-            minifyEnabled false
-            shrinkResources false
+            minifyEnabled true
+            shrinkResources true
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
     }

app/proguard-rules.pro

@@ -15,7 +15,9 @@
 # Uncomment this to preserve the line number information for
 # debugging stack traces.
 #-keepattributes SourceFile,LineNumberTable
+-dontobfuscate
 
 # If you keep the line number information, uncomment this to
 # hide the original source file name.
 #-renamesourcefileattribute SourceFile
+-keep class org.mosad.seil0.projectlaogai.util.** { <fields>; }

app/src/main/java/org/mosad/seil0/projectlaogai/controller/cache/TimetableController.kt

@@ -34,7 +34,9 @@ import org.mosad.seil0.projectlaogai.util.TimetableWeek
  * and lessonMap objects. It also contains the additional subjects logic.
  * All functions ro read or update cache files are located in the CacheController.
  *
- * TODO add configurable week to addSubject() and removeSubject(), updateAdditionalLessons()
+ * TODO
+ *  * add second week
+ *  * add configurable week to addSubject() and removeSubject(), updateAdditionalLessons()
  */
 class TimetableController {