replay: add replay module, build for sitl_default, but do not load on startup

This adds a new module that does:
- read an parse an ULog file, given via ENV variable 'replay'
- apply all parameters from the log file
- read and apply user-defined override parameters from a file
- publish all messages in 'real-time' from the log file and add a constant
  offset to the timestamp to match the system time.
- apply changed parameters in the log (which are not overridden)

Tools/check_code_style_all.sh

@@ -31,6 +31,7 @@ find \
     src/modules/muorb \
     src/modules/param \
     src/modules/px4iofirmware \
+    src/modules/replay \
     src/modules/segway \
     src/modules/sensors \
     src/modules/simulator \