Feature/comments and buffer checks (#73)

* Added comments

* Replaced Goto construct

* Added apdu_len check

* Added comments

* Added string limit and reworked printable check

* Mainly comments

* Just comments

* Just comments

* decode service request returns now non zero on success

* eliminated warnings

* Added character string init with length check.

* Paranoic length check

* Comments and object index checking on read/write.

* Check name/desc strings before returning.

* Eliminated Goto

src/bacnet/bacstr.h

@@ -120,6 +120,10 @@ extern "C" {
     bool characterstring_init_ansi(
         BACNET_CHARACTER_STRING * char_string,
         const char *value);
+    bool characterstring_init_ansi_safe(
+        BACNET_CHARACTER_STRING * char_string,
+        const char *value,
+        size_t tmax);
     bool characterstring_copy(
         BACNET_CHARACTER_STRING * dest,
         BACNET_CHARACTER_STRING * src);