This app is not yet properly working, it doesn't always properly set time.
To be checked out exactly why.

Previously, this function was returning a human-friendly version of the
time received from GPS. This was now optimized to make it easire to operate
with other programming structures (e.g., struct tm). This modification has the
added benefit of returning the exact values received via the GPRMC NMEA
sentence.

Two more events were added to the event type (event.h)
- GPS_TICK -- tick from GPS background task
- GPS_OFF  -- to signal the status bar that the GPS was turned off,
so it can remove the icon

The status bar and GPS coordinate app were changed to react to the
proper events, i.e., both events above in the case of the status bar
and the GPS_TICK event in the case of the GPS coordinate app.

Tested with the GPS coordinate style in gpscoord.c

Not yet tested, hence the new branch

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