timeActivatedFileUpdate FO takes two iterations to come into effect

(Exchange 358)

• time to activate is exact so e.g. if time = 4.9999999 and activate time is set as 5 it will not trigger

• checking for changed files is done before executing FOs so change of file is not picked up until next time step

• improvement: forcibly re-check modified files in timeActivatedFileUpdate:

    cp(timeVsFile_[i].second(), destFile);
    mv(destFile, fileToUpdate_);
    lastIndex_ = i;
    const_cast<Time&>(time_).Time::readModifiedObjects();

(make sure to call Time::readModifiedObjects, not objectRegistry one)

• other: if updated files are themselves FOs these need to do their action in their 'read' function or constructor. Alternative would be to know which FOs are new and execute only these. This sounds too convoluted.