walk back i18n_component filter; introduce /identifier/:id instead

while i18n_component is technically more in-line with the existing data
it also means unnecessary porting for a potential v2 so instead
soft-deprecate the previous kinda conflicting id filter and rename it
to basename. this then frees things up for calling the identifier actually
identifier. furthermore since identifier is global unique there's no point
in having clients issue a find and then a /project/:path when that is
exactly the same amount of work we need to do anyway.

so instead add a new /identifier/:id endpoint which returns the relevant
project in one go