some refactoring

[jmlich]

I was trying to find out reason why the SportSummaryPage is rendered slowly. I have improved code a little. Here are changes explained one by one

Amazfish::activityToString:

• multiple if() changed to switch(). I think it is easier to read and easier for compiler to optimize.

HeartratePage.qml:

• I was confused, because SportsSummary page is loaded already when Heartrate page is shown
• var -> real - for qml compiler are optimizations easier
• var point = points[i]; In my other project I have spotted significant performance improvement. However, doesn't feel better.

SportsSummaryPage.qml:

• listItem.width -> it was hard to read for me until I figured out that is belongs to previous line.

SportsDataModel::data()

• I have changed condition if (index.row() < 0 || index.row() > m_data.length()) { to return early, because I don't like code which is indenting into the deepness.
• I have switched if to switch-case
• I have used separate variable const SportsData &item = m_data.at(index.row()); to improve readability.

sportsdatamodel.cpp:

• the bottleneck is "here", so I have added QElapsedTimer, but I guess this is not available in Qt 5.6, so I have removed it
• the query usually took less than 0.2 seconds
• my finding is that SportsDataModel::update() takes ~2 seconds on endResetModel(); line. I guess, this means that rendering of updated model is slow.
• I have tried to comment out some items (timeImage, timeLabel, distanceImage, distanceLabel) in delegate and it really helped, but this is task for future myself.

[piggz]

brilliant, thanks!