Refactor ConcurrentMap

* Add operator[] to ConcurrentMap which returns a TValue reference
* BTTV/FFZ channel emotes are now stored in the Emote Manager, and each Channel object has a reference to their own BTTV/FFZ channel emote map.
* Restructure EmoteManager a bit (simplify the ConcurrentMap havoc).
* Add EmoteData struct which can store emote data (for now only messages::LazyLoadedImage*)
* Add CompletionManager that does nothing

chatterino.pro

@@ -95,7 +95,8 @@ SOURCES += \
     src/widgets/accountpopup.cpp \
     src/messagefactory.cpp \
     src/widgets/basewidget.cpp \
-    src/widgets/resizingtextedit.cpp
+    src/widgets/resizingtextedit.cpp \
+    src/completionmanager.cpp
 
 HEADERS  += \
     src/asyncexec.hpp \
@@ -155,7 +156,8 @@ HEADERS  += \
     src/widgets/accountpopup.hpp \
     src/util/distancebetweenpoints.hpp \
     src/messagefactory.hpp \
-    src/widgets/basewidget.hpp
+    src/widgets/basewidget.hpp \
+    src/completionmanager.hpp
 
 PRECOMPILED_HEADER =