Playlists were treated as platforms due to typos. Likely broke AM
taglists, but had no sideffects for LB platforms as modifiedPlaylists()
was being used before playlists were added, and seemingly didn't affect
LB playlists either as the null playlist ID would cause the check
functions to think the bogus playlists had already been handled due to
the platform entries in Parents.xml

Previous max of -1 was a leftover from the previous implementation of
Qx::FreeIndexTracker who's index type was templated, so -1 represented a
reasonable max (likely 32-bit integer limit); however, now that the
tracker uses quint64 for indexing, -1 was interpreted as the maximum
value for 64-bit integers and caused allocaiton of its internal bit-
array to fail due to absurd size requirements.

This was undiscovered due to the previous playlist bugs.

Accidentally was calling release() instead of reserve().

No need to store as a QHash with the playlist name as the key since the
name is not needed. This also avoids the awkwardness that is the
conversion between the original playlist name and the translated name,
specific to LB. Before, playlists with names that differed between their
original and translated names were not being added to the Flashpoint
platform category as the keys in the hash were the pre-translated names,
while the list checked against at the end were the translated names.

Fix some playlists not being included under the Flashpoint Platform Category in LaunchBox

Frontends often use modifiedPlatforms()/modifiedPlaylists() to check
which Platforms/Playlists were affected by the important and need to be
taken into account by other parts of the frontend; however, this
obviously only applies if the doc was stricly modified and not outright
removed, which can happen if the commited modified doc is empty.

This change ensures that only modified docs that remain will be part of
the modified list.

Needed for some ImportWorker tasks

LB, the only platform that supports them currently, already has its own.
Will need to revisit this if other platforms that support them are
added.

…egories

LB: Nest platforms and playlists under their own platform categories