Some of the GPX end tags were missing the '/' corresponding to XML end tags
and this meant websites such as OpenStreetMap [1] or MapBBCode [2] could not
import the GPX files created using test_covert_files.

The tags were added and now these sites can import our GPX traces.

[1] openstreetmap.org
[2] http://share.mapbbcode.org

converter reverse (from raw data from file to GPS data)
converter from GPS data to GPX format

SD via SPI : works thanks to efm32 implementation. We use fatfs to implement FAT32 (instead of FAT-SL)
Project sw/os-comparison/an0030_efm32_fat_on_sd_card compiles and run the FAT32 : it writes a file on the microSD

Functions of SD are implemented in ../common/drivers/sd.c and ../common/drivers/sd.h to be OS-independent

added SPI implementation provided by EnergyMicro , created file for implementing driver FAT on SD through SPI

now it doesn't produce a valid binary (compliation is ok but file is too big)

Signed-off-by: Theodor Stana <t.stana@cern.ch>