Adapt anonymizaion code to read CPET

[skeating]

From #47

[skeating]

• [x] read xml
• [x] find appropriate fields
• [x] anonymize age
• [x] remove any other identifiable data
• [x] shift time frame

[skeating]

this is almost done, Sarah to provide a sample input and output for @nikk-nikaznan to do the necessary tweaks to the code