however, there is no consumer level software for the network yet.
Not true.
There are a lot of LApps (Lightning Apps)
available already And new ones are being
introduced everyday If so, who's creating these apps?
Different developers are.
You don't need anyone's permission to create a LApp.
Just read the
developer's guide to get started.
Is the core team working on an implementation of an app similar to bitcoin-qt?
There is no "core team" per se.
There's no reference implementation for Lightning.
There are different groups of developers working on different implementations of the Lightning Network, but they are designed for interoperability.
There's Blockstream's
c-lightning, Lightning Lab's
LND written in Go,
ACINQ's Eclair written in Scala, lit, lightning-onion, etc.
Each implementation has its own desktop interface á la Bitcoin-Qt:
There's Zap wallet, LND-GUI, Eclair, etc.
Most are cross-platform and there are also mobile (Android) apps for Lightning eg Eclair -- even though it's on the testnet now.
There are also
browser extensions, And
web wallets