peer dependency for easier overriding
rename
add i18nliner-compatible processor

auto-register it with the Command, so we get check/export for free
allow explicit keys in block calls
allow Extractor to be overridden, pass context back up
little refactor so that t_call has useful properties (e.g. line)
a couple plumbing tweaks

allow TCall to be swapped out, and pass some more useful context back up
split this into two methods for easier customization
v0.0.3