Fix app manager fail to install large app file issue (#555)

Remove the limit of app file size no larger than 1 MB, fix possible memory leak issues when fail to install app file, change message size of aee_host_msg_callback() from uint16 type to uint32 type to fix possible integer overflow issue, and fix some coding style issues of app manager.

Signed-off-by: Wenyong Huang <wenyong.huang@intel.com>

core/app-mgr/app-manager/watchdog.h

@@ -31,6 +31,9 @@ app_manager_get_watchdog_timer(void *timer);
 bool
 watchdog_startup();
 
+bool
+watchdog_destroy();
+
 #ifdef __cplusplus
 } /* end of extern "C" */
 #endif