SCH_Lab table definition uses CFE_SB_MsgId_t type without including header for it

[jphickey]

Describe the bug
All Code compilation units should explicitly #include the headers for all types/macros/functions which are directly used by that unit.

The "sch_lab_sched_tab.h" defines a structure that depends on CFE_SB_MsgId_t, but it does not include the header that provides this type.

To Reproduce
Compilation fails when building with the ic-ccb-20191009 branch, which includes a change that causes the definition of CFE_SB_MsgId_t to no longer be implicitly included.

apps/sch_lab/fsw/platform_inc/sch_lab_sched_tab.h:63:5: error: unknown type name ‘CFE_SB_MsgId_t’
     CFE_SB_MsgId_t  MessageID[SCH_LAB_MAX_SCHEDULE_ENTRIES];  /* Message ID for the table entry */
     ^~~~~~~~~~~~~~

Expected behavior
The build should complete successfully.

System observed on:
Ubuntu 18.04.2 LTS 64 bit (build host)

Reporter Info
Joseph Hickey, Vantage Systems Inc.