Fix nasa#711, Add message header module

Implements message header module such that users
can customize or extend as needed.
 - Separates code for easier selection
 - Implements consistent getter/setter APIs
 - Fix nasa#736/nasa#781: MsgId logic no longer overrides bits in init
 - Fix nasa#529: Get size supports max size
 - Adds single big endian time implementation, but not selected
 - Adds msg module to module list
 - Adds msg module to cppcheck

.travis.yml

@@ -17,8 +17,8 @@ script:
   # Check versions
   - cppcheck --version
 
-  #cppcheck flight software cfe/fsw/cfe-core/src
-  - cppcheck --force --inline-suppr --std=c99 --language=c --error-exitcode=1 --enable=warning,performance,portability,style --suppress=variableScope --inconclusive fsw/cfe-core/src 2>cppcheck_flight_cfe.txt
+  #cppcheck flight software fsw/cfe-core/src and modules
+  - cppcheck --force --inline-suppr --std=c99 --language=c --error-exitcode=1 --enable=warning,performance,portability,style --suppress=variableScope --inconclusive fsw/cfe-core/src modules 2>cppcheck_flight_cfe.txt
   - |
     if [[ -s cppcheck_flight_cfe.txt ]]; then
       echo "You must fix cppcheck errors before submitting a pull request"

cmake/mission_defaults.cmake

@@ -14,6 +14,7 @@ set(MISSION_CORE_MODULES
     "cfe-core" 
     "osal"
     "psp"
+    "msg"
 )
 
 # The "MISSION_GLOBAL_APPLIST" is a set of apps/libs that will be built