logic: allow the user to discard an aborted indexer run

* keep old database on filesystem while indexing
* migrate old ".coatiproject" settings to new ".srctrlprj" extension when loading project
* send new errors in MessageErrorCountUpdate after injecting
* recheck filepath exist() in FileSystem's remove, rename, copy and create functions
* updated tasks to new "override" policy

src/lib/utility/messaging/filter_types/MessageFilterErrorCountUpdate.h

@@ -21,6 +21,15 @@ class MessageFilterErrorCountUpdate
 			{
 				if ((*it)->getType() == MessageErrorCountUpdate::getStaticType())
 				{
+					MessageErrorCountUpdate* frontErrorsMessage = dynamic_cast<MessageErrorCountUpdate*>(message);
+					MessageErrorCountUpdate* backErrorsMessage = dynamic_cast<MessageErrorCountUpdate*>(it->get());
+
+					backErrorsMessage->newErrors.insert(
+						backErrorsMessage->newErrors.begin(),
+						frontErrorsMessage->newErrors.begin(),
+						frontErrorsMessage->newErrors.end()
+					);
+
 					messageBuffer->pop_front();
 					return;
 				}

src/lib/utility/messaging/type/error/MessageErrorCountUpdate.h

@@ -14,13 +14,20 @@ public:
 		return "MessageErrorCountUpdate";
 	}
 
-	MessageErrorCountUpdate(const ErrorCountInfo& errorCount)
+	MessageErrorCountUpdate(const ErrorCountInfo& errorCount, const std::vector<ErrorInfo>& newErrors)
 		: errorCount(errorCount)
+		, newErrors(newErrors)
 	{
 		setSendAsTask(false);
 	}
 
+	virtual void print(std::wostream& os) const
+	{
+		os << errorCount.total << '/' << errorCount.fatal << L" - " << newErrors.size() << L" new errors";
+	}
+
 	const ErrorCountInfo errorCount;
+	std::vector<ErrorInfo> newErrors;
 };
 
 #endif // MESSAGE_ERROR_COUNT_UPDATE_H