ParseReqsInDirectory doesn't exclude stray sub-REQs

[marth8880]

If a side (for example) is added to the list and there are REQs in its asset directory that aren't listed in the side's main REQ's LVL chunk, those REQs are added to the Munged Files list.

EXPECTED:

Sub-LVLs and stray REQs are excluded from the Munged Files list.

[marth8880]

Problem with fixing this is the whole point of adding stray REQs that aren't listed as sub-LVLs, which is to make it so a user can add a world that has multiple LVLs (e.g., the main LVL and a sky LVL).

Might create a fix for this that doesn't apply to munging worlds, but putting on the backburner for now.

[marth8880]

Issue fixed in 69ef51d - closing.