data: indexer processes

* TaskBuildIndex starts seperate indexer processes and communicates via shared memory
* indexer processes get restarted if they fail
* indexer processes are killed when the app closes or crashes
* added utility class SharedMemory to allocate and access shared memory, providing basic data structures
* added SharedMemoryGarbageCollector for keeping track of running instances and cleaning up shared memory in case of a crash
* show errors for source files that crashed during indexing
* added basic exception handling to task scheduling
* added option to turn off processes and use threads in preferences, but still use shared memory

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src/lib/Application.h

@@ -34,6 +34,8 @@ public:
 	static std::shared_ptr<Application> getInstance();
 	static void destroyInstance();
 
+	static std::string getUUID();
+
 	static void loadSettings();
 	static void loadStyle(const FilePath& colorSchemePath);
 
@@ -53,6 +55,7 @@ public:
 
 private:
 	static std::shared_ptr<Application> s_instance;
+	static std::string s_uuid;
 
 	Application(bool withGUI=true);