<rdar://problem/11914077>

If you type help command <word> <word> <word> <missingSubCommand> (e.g. help script import or help type summary fake), you will get help on the deepest matched command word (i.e. script or type summary in the examples)
Also, reworked the logic for commands to produce their help to make it more object-oriented



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@183822 91177308-0d34-0410-b5e6-96231b3b80d8