Event Handler

Similar to text handler, pull out the disparate array of functions which format information from an event ready for display in the UI and put in a handler class with a test suite.

requires https://github.com/quotient-im/libQuotient/pull/686

autotests/CMakeLists.txt

@@ -26,3 +26,9 @@ ecm_add_test(
     LINK_LIBRARIES neochat Qt::Test
     TEST_NAME mediasizehelpertest
 )
+
+ecm_add_test(
+    eventhandlertest.cpp
+    LINK_LIBRARIES neochat Qt::Test
+    TEST_NAME eventhandlertest
+)