- implement memory aware flushing;
- share node cache across multiple indexes;
- implement write stalling;
- avoid to allocate large buffers when store.maxValueSize is too large.
coverage: 89.5% (+0.005%) from 89.495%
when pulling 986deea3c4d779ccbea16dd8c0d6a336f24bb9e3 on ostafen:index-shared-resources
into c0b6e0122acc86948819e596182728b12cdea625 on codenotary:master.