Detect and ignore #q2:types rows in standalone metadata input

[fedarko]

Standalone Songbird doesn't understand these rows, so it'll interpret them as actual samples (messing things up slightly). This is already documented in the README, but it'd be good to automatically handle these situations.

I wrote a function in Qurro that should handle this -- see e.g. this part of code. can take a crack at incorporating this into songbird.

[mortonjt]

Yes! Great idea