utils/checkpackagelib: CommentsMenusPackagesOrder: separate comment/if/menu cases

utils/checkpackagelib: CommentsMenusPackagesOrder: separate comment/if/menu cases

The handling of 'comment...', 'if ...' and 'menu ...' lines have almost
nothing in common, and subsequent patches will give them even less in
common. Therefore, completely separate their handling in top-level
conditions. The only code that gets duplicated in the different branches
is the 'self.initialize_level_elements(text)' call.

Signed-off-by: Jerzy Grzegorek <jerzy.m.grzegorek@gmail.com>
Cc: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Reviewed-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>