Tests: tune codecov configuration

Turns off a comment to each pull request about the overall coverage status but keeps the comment about the change in coverage the pull request introduces when merged.
Group the coverage reports by components (flags) to be seen on the codecov.io website.

.codecov.yml

@@ -2,6 +2,11 @@ codecov:
   notify:
     require_ci_to_pass: yes
 
+coverage:
+  status:
+    project: off
+    patch: on
+
 comment:
   layout: "diff, files"
   behavior: default
@@ -9,7 +14,25 @@ comment:
   require_base: no        # [yes :: must have a base report to post]
   require_head: yes       # [yes :: must have a head report to post]
 
-# don't gather statistics for tets and external libraries
+flags:
+  # filter the folder(s) you wish to measure by that flag
+  api:
+    paths:
+      - api/
+  library:
+    paths:
+      - lib/
+  client:
+    paths:
+      - client/
+      - clientgui/
+  server:
+    paths:
+      - sched/
+      - db/
+      - tools/
+
+# don't gather statistics for test and external libraries
 ignore:
   - tests/.*
   - zip/.*