Converted to Python 3, added csvonly data format

[v01dma1n]

Hi,
Thanks a bunch for the script!
To adapt it to my needs, I added 'csvonly' data format value, which suppresses downloading GPX data and retrieves activities to CSV file only.
While doing this, I converted the script to Python 3.
Irek

[kjkjava]

Hi Irek,

Thanks for the contribution! Do you know if these Python 3 changes will still work the same under Python 2.7?

Thanks,
Kyle

[v01dma1n]

Not a Python buff... Sorry... duno.

[v01dma1n]

Did some reading about this whole Python 2 vs. Python 3 story and the change for 'csvonly' does not rely on anything Python 3 specific.
On the other hand, I liked the changes proposed by lefty01 related to using argparse.
So, if you decide to merge his changes, could you remember about 'csvonly'?
Thanks a bunch again!

[djacobson]

Just a note, I really like this example. I discovered that Garmin has changed their download URLs (yes, again) to the following format:

'http://connect.garmin.com/modern/proxy/download-service/export/gpx/activity/{0}'
...