When using fulltext only search, then only the index must be searched.
This wasn't working anymore, because the routes added a query to
always select valid items (those not being processed). But this lead
to the downstream code to always consult the database, too. Since the
routes are using a "simple-search" interface, this is now adding the
valid-state condition if applicable. There are still more low-level
interfaces that can be used when searching should be done differently.
Closes: #823
- put all used strings in one place to have it easier to track
- don't use `$` for shortcuts, it's a detail not interesting to a
user; now names must not clash (which is a good idea anyways)
- Added two more shortcuts `conc` and `corr`
