Include stdint in cellular types header file (#53)

* Update cellular library to MIT license

* Include stdint in cellular types header file

* Include stdint for uint8_t, uint32_t ....
* Remove cellular_common.h include in cellular_api.h. Cellular common is
  designed to be used by cellular module porting.

* Fix spelling check

Author: chinglee-iot

source/include/cellular_api.h

@@ -38,7 +38,6 @@
 
 /* IoT Cellular data types. */
 #include "cellular_types.h"
-#include "cellular_common.h"
 
 /* Hardware interface. */
 #include "cellular_comm_interface.h"

source/include/cellular_types.h

@@ -36,7 +36,9 @@
 #endif
 /* *INDENT-ON* */
 
+/* Includes for standard bool and int. */
 #include <stdbool.h>
+#include <stdint.h>
 
 /**
  * @ingroup cellular_datatypes_paramstructs