readded and fixed #4781: new cache size nano (commit b300630 got lost)

compatibility:
- is supported by new OKAPI rev. 495
- Ocprop compatibility is being checked
- is returned as "other" size in XML interface size field, and as "nano" in new size2 field
- is returned as Micro in GPX files
changed nano size XML implementation

and implemented clean XML versioning for new features
additional waypoints and personal note in gpx files, based on Schrottie
code
fixed and improved gpx child waypoints
added picture links to GPX files
revised data privacy statement
Merge branch 'dsb'
finalized release 3.0.4 / changlog