Allows to speed up lookups like "is property FOO of data BAR animated".
Can be used to optimize object's visibility check, but also allows to
check animation on bones without too much of time penalty.
The cache is shared between both nodes and relations builder.
Currently is not used, just a boilerplate for an upcoming changes in
an actual logic.
Is mainly used by drivers variables. The slow part was about
iterating over all pose channels to find the one which has a
given constraint.
Now we build a look up table, so this operation is way cheaper,
Brings down relations update time from 0.7sec to 0.4 with Spring
production file.
