[ground_segment] put google maps dir in Google subdir in var/maps

should close #902
[conf] example on how to use SPEECH_NAME
add *.hgt files in srtm folder to gitignore

closes #900
[simulator] NPS: add --time_factor command line option
[nps] always define USE_MISSION_COMMANDS_IN_NPS if mission_rotorcraft module is loaded
Fix bug in datalink
[modules] add digital_cam_shoot_rc.xml

module to use radio channel as remote camera trigger
closes #937
[messages] add INFO_MSG and print it to GCS console

Uses a separate string_of_chars function for now to convert the
char array from ivy (e.g. |i,n,f,o, ,m,s,g|) to normal string to
nicely write to console and messages app.

Proper solution would be to write char arrays as normal "quoted string" to the ivy bus.
[JTAG][BMP] latest blackmagic firmware easy to update from within paparazzi: closes #871
[ocaml][messages] use quotes for char arrays

- char[] are now treated as 'real' strings
- no more delimiters for other arrays (where space characters should not
  appear)
[ocaml] backward compatibility on old array's delimiters
[python] update messages tool to deal with whitespaces in arrays
[filters] add missing include to low_pass_filter.h
[modules] fix some more modules after conversion to telemetry functions
[conf] add aispeed_ms45xx_i2c module to Quad_Navstik

for testing
Merge pull request #942 from paparazzi/ivy_arrays

Remove array delimiters on Ivy messages
[build] quiet output on clean_ac
[tests] option to show warnings even if successfully compiled

Examples on how to test compile all aircrafts/targets in your current conf.xml:
with parallel compilation and showing full output during compilation
 $ J=AUTO prove tests/examples -v
only showing full compile output if there has been an error, if there were warnings only print those
 $ SHOW_WARNINGS_ONLY=1 prove test/examples
with parallel compilation and treating all warnings as errors:
 $ J=AUTO USER_CFLAGS=-Werror prove tests/examples
update travis config to show warnings
install libipc-run-perl in travis setup