This is a follow-up to 399d4ef8

This makes it possible to use the 'motor_test' command

This happens for example if no SD card is present.

The reason for this change is that RPi2 and RPi3 are compatible, and
hopefully all differences coming up can be resolved without ifdefs but
at runtime.

We currently only support Navio2, so let's fuse the two configurations.

The two cmake files for default and release where out of
sync. This change bases them on a common cmake file.

* logger: disable some default topics, which are most likely not used

This is also to safe CPU and lower the amount of file descriptors used.

* logger: use the hrt timer for more accurate scheduling

Under NuttX with the default rate of 285Hz, the actual measured rate was
only 200Hz while on Linux it was ~280Hz. The reason is that NuttX only
uses a usleep() granularity of 1ms, so that the typical sleep time is
longer than what we set.

Now the logger waits on a semaphore, which gets activated periodically
with a hrt timer. With this the measured rate is exactly the expected one,
285Hz.

Fixedwings need a global position estimate for POSCTL.

We want to allow flying POSCTL with optical flow only without GPS.

Small additions for Intel Edison.

They're initialized in do_gyro_calibration already

This fixes the issue where the console was spammed if a broadcast failed
after a connection had previously been established.

This fixes a bug with following setup:
- two (or N > 1) connected gyros
- ekf2 enabled
In this case, sensors would publish with the combined rate of the gyros,
but with N following messages having the same gyro data & timestamp.
Apparently ekf2 cannot handle this, the other estimators can.

We may want to rethink what the proper solution is here.