ShellPkg: Ease the shell's MAN file Title Header syntax requirements.

ShellPkg: Ease the shell's MAN file Title Header syntax requirements.

Prior to this change, the shell would not use a MAN file if the Title Header line was not strictly formatted.
For example, if the case of the command name in the file was not exactly the same as the case of the command name as typed by the user,
the MAN file would not be used.  Also, extra whitespace on the line would also cause the shell to ignore the MAN file.
This change allows "extra" white space and ignores case when looking for the command name.
It also ignores any path information for cases where the user enters a relative or absolute path to the EFI file.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jim Dailey <jim_dailey@dell.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19290 6f19259b-4bc3-4df7-8a09-765794883524