First Person KML using wrong decimal separator

#### Issue details
_Please describe the problem, or desired feature_
After clicking "First Person KML" button, a KMZ file is generated. Inside the KML file within the KMZ file, each gx:FlyTo tag has a gx:duration tag. This gx:duration tag has a float number string, which is generated (I suppose) using the Operating System default decimal separator. For OS where the deafault decimal separator is not a dot (.), the result is a invalid KML number. For me, the file has a 0,1 tag (note the coma), since I'm using a Brazillian MS Windows. Google Earth ignores this tag, resulting in an empty "tour". This probçpem does not occur for other number, like: longitude, altitude, roll or heading. Mission Planner should use a dot (.) regardless of the OS default decimal separator.
By the way, the "First Person KML" button should not be inside the "Download dataflash log via mavlink". window. It is not related nor depends on this window. This button should be besides "review a log" button. The same for "recreate kml" and ".bin to .log".

#### Version
_What version was the issue encountered with_
1.3.49

#### Platform
[ ] All
[ ] AntennaTracker
[X ] Copter
[ ] Plane
[ ] Rover
[ ] Sub

#### Airframe type
_What type of airframe (flying wing, glider, hex, Y6, octa etc)_
Quad
#### Hardware type
_What autopilot hardware was used? (pixhawk, pixracer, PX4FMU etc)_
Pixhawk
#### Logs
_Please provide a link to any relevant logs that show the issue_

Start with the Mission Planner "First Person KML" button using a Brazilian Windows locale, then inspect the generated KMZ's KML and its gx:duration values. Done means Google Earth recognizes the tour with a dot decimal separator, and the First Person KML, recreate KML, and .bin to .log buttons are placed beside "review a log" rather than in the dataflash download window.

Written by the indexing model from the issue text.