Write a file `uuid` in server's data directory that contains random UUID, generated at startup if file does not exist.

It will be used for several purposes:
- to anonymously identify server in Sentry (currently Sentry is unusable);
- (possible future usage) to identify server in ensemble.

@tavplubix comments?
void registerFunctionBlockNumber(FunctionFactory &);
void registerFunctionRowNumberInBlock(FunctionFactory &);
void registerFunctionRowNumberInAllBlocks(FunctionFactory &);
void registerFunctionNeighbor(FunctionFactory &);
void registerFunctionSleep(FunctionFactory &);
void registerFunctionSleepEachRow(FunctionFactory &);
void registerFunctionMaterialize(FunctionFactory &);
void registerFunctionIgnore(FunctionFactory &);
void registerFunctionIndexHint(FunctionFactory &);
void registerFunctionIdentity(FunctionFactory &);
void registerFunctionArrayJoin(FunctionFactory &);
void registerFunctionReplicate(FunctionFactory &);
void registerFunctionBar(FunctionFactory &);
void registerFunctionHasColumnInTable(FunctionFactory &);
void registerFunctionIsFinite(FunctionFactory &);
void registerFunctionIsInfinite(FunctionFactory &);
void registerFunctionIsNaN(FunctionFactory &);
void registerFunctionIfNotFinite(FunctionFactory &);
void registerFunctionThrowIf(FunctionFactory &);
void registerFunctionVersion(FunctionFactory &);
void registerFunctionBuildId(FunctionFactory &);
void registerFunctionUptime(FunctionFactory &);
void registerFunctionTimezone(FunctionFactory &);
void registerFunctionTimezoneOf(FunctionFactory &);
void registerFunctionRunningAccumulate(FunctionFactory &);
void registerFunctionRunningDifference(FunctionFactory &);
void registerFunctionRunningDifferenceStartingWithFirstValue(FunctionFactory &);
void registerFunctionRunningConcurrency(FunctionFactory &);
void registerFunctionFinalizeAggregation(FunctionFactory &);
void registerFunctionToLowCardinality(FunctionFactory &);