* feature: we can check if a fileId is already in the cache
We using this to protect cache from adding the same needle to
the cache over and over.
* fuse mount: Do not start dowloader if needle is already in the cache
* added maxFilePartSizeInCache property to ChunkCache
If file very large only first maxFilePartSizeInCache bytes
are going to be put to the cache (subject to the needle size
constrains).
* feature: for large files put in cache no more than prescribed number of bytes
Before this patch only the first needle of a large file was intended for
caching. This patch uses maximum prescribed amount of bytes to be put in
cache. This allows to bypass default 2MB maximum for a file part stored
in the cache.
* added dummy mock methods to satisfy interfaces of ChunkCache
dab0bb8097