Slightly rename EMPER: s/Extensible/Efficient/

While extensibility is still a feature of EMPER, a more important
aspect is its efficiency.

README.md

 # EMPER
 
-The Extensible Massive-Parallelism Execution Realm (EMPER) is a concurrency platform to develop and execute parallel applications.
+The Efficient Massive-Parallelism Execution Realm (EMPER) is a concurrency platform to develop and execute parallel applications.
 
 EMPER's primary objective is to support the research of different aspects of parallel execution of a potentially massive amount of concurrent strands of execution on current and future many-core systems.
 Those aspects include, for example, scheduling strategies, synchronization primitives, and ultimately the overall coordination of concurrent strands of execution concerning optimal resource usage, including locality and energy efficiency.

emper/Emper.cpp

@@ -117,7 +117,7 @@ auto operator>>(std::istream& in, ContinuationStealingMadviseStack& cont_stealin
 
 void printInfo(std::ostream& strm) {
 	// clang-format off
-	strm << std::boolalpha << "Extensible Massive-Parallelism Execution Realm (EMPER)" << std::endl
+	strm << std::boolalpha << "Efficient Massive-Parallelism Execution Realm (EMPER)" << std::endl
 			 << "Version: " << getFullVersion() << std::endl
 			 << "Debug: " << DEBUG << std::endl
 			 << "IO: " << IO << std::endl