Add new cache capabilities method(s)

[following5]

When designing services/caches/capabilities, I missed that capabilities can be withdrawn. E.g. OCPL already allows to disable cache sizes. A disabled size can no longer be assigned to caches, but can still be present with existing caches.

So there can be different capabilities for submitting cache data than for searching. This applies to:

• cache types
• cache sizes
• cache countries and regions (not released yet - #570)
• cache desc languages (not released yet - #570)

The is NO problem with:

• cache statuses - search-only capability, cannot be directly edited
• has_ratings - search-only capability, cannot be directly edited
• password_max_length - edit-only capability, not seachreable

This may be solved by splitting between

• services/caches/capabilities (submitting)
• services/caches/search/capabilities (searching)

Search capabilities would be the union of all existing and historic submit capabilties. Additionally, we could supply information about existing cache properties, so that developers can optimize user interfaces by hiding unused options.

(Note that there is no issue with services/logs/capabilities, which are defined for submitting/editing logs only. Also there is no issue with editing caches or logs that have redrawn properties, e.g a no longer allowed cache sizes - both methods allow to retain them.)

This issue blocks #570.

[following5]

This is critical because the interface is flawed, but not in use yet. Should fix before anyone uses it.

[following5]

Removed services/caches/capabilities by 72e03f7.