Initial Matomo integration.

.github/CONTRIBUTING.md

@@ -55,19 +55,18 @@ You'll have to:
 
 - Define some parameters either in `~/.gradle/gradle.properties` or as gradle parameters (see the examples)
 
-    - appLoginUrl, appLoginUsername and appLoginPassword: url, username and password of a selfoss instance. **These are only used for tests. They can be empty if you don't test API calls.**
+    - matomoUrl and matomoSite: url and siteId for a matomo instance
 
 ### Examples:
 #### Inside ~/.gradle/gradle.properties
 
 ```
-appLoginUrl="URL" # It can be empty.
-appLoginUsername="LOGIN" # It can be empty.
-appLoginPassword="PASS" # It can be empty.
+matomoUrl="URL" # It can be empty.
+matomoSite="1" # It can be empty, but needs to be an integer
 ```
 
 #### As gradle parameters
 
 ```
-./gradlew .... -P appLoginUrl="URL" -P appLoginUsername="LOGIN" -P appLoginPassword="PASS"
+./gradlew .... -P matomoUrl="URL" -P matomoSite="1"
 ```