idea: DTO for updating entry cache should also include number of entries

[rmunn]

Is your feature request related to a problem? Please describe.
Sometimes the entry cache is incomplete, and Language Forge doesn't detect that situation. This can lead to users being afraid that they've lost data, because they only see 6 entries when there should be 31.

Describe the solution you'd like
We could have the entry update DTO send a count of the entries the server knows about. Then when the client has finished applying the update (including any new entries), check if the entry counts match. If they don't match, discard the current cache and re-download the entire dictionary from the server again.

Describe alternatives you've considered
The "reset browser cache" button that we've placed in the advanced configuration page allows redownloading the dictionary, but that's a manual process. We'd like to automatically catch the situation and fix it.

Additional context
#1024 is an older issue related to incomplete-cache problems; this may be a duplicate of that one, or it might turn out this is a different idea and #1024 should be kept around.