version cleanup: move all version information into version.c and use a common API

The provided versioning information is the same, except for some additions,
like OS version (which still need to be implemented on NuttX).

src/modules/logger/logger.cpp

@@ -1361,7 +1361,7 @@ void Logger::write_header()
 /* write version info messages */
 void Logger::write_version()
 {
-	write_info("ver_sw", PX4_GIT_VERSION_STR);
+	write_info("ver_sw", px4_firmware_version_string());
 	write_info("ver_hw", px4_board_name());
 	write_info("sys_name", "PX4");
 	int32_t utc_offset = 0;

src/modules/logger/logger.h

@@ -39,7 +39,6 @@
 #include <drivers/drv_hrt.h>
 #include <uORB/Subscription.hpp>
 #include <version/version.h>
-#include <systemlib/git_version.h>
 #include <systemlib/param/param.h>
 
 extern "C" __EXPORT int logger_main(int argc, char *argv[]);