clientmap, clientmedia: code modernization

* use range-based for loops
* simplify some tests
* various code style fixes
* remove debugprint in ClientMap::getBackgroundBrightness, debug code was not intended to be there
* remove unused fields in MapDrawControl
* use emplace_back instead of push_back when necessary

src/clientmedia.h

@@ -42,10 +42,10 @@ public:
 
 	float getProgress() const {
 		if (m_uncached_count >= 1)
-			return 1.0 * m_uncached_received_count /
+			return 1.0f * m_uncached_received_count /
 				m_uncached_count;
-		else
-			return 0.0;
+
+		return 0.0f;
 	}
 
 	bool isStarted() const {