Cherry-picking changes:
c503e736 2019-07-02 yiwu@pingcap.com     Fix Titan portable build (#312)
c17648a5 2019-07-01 yiwu@pingcap.com     Fix create_cf not passinig titan specific options to titan (#311)

* Fix titan config (#306)

* Add titan read option (#309)
Signed-off-by: Connor1996 <zbk602423539@gmail.com>

Signed-off-by: Yi Wu <yiwu@pingcap.com>

Signed-off-by: siddontang <siddontang@gmail.com>

* add recycle log configuration
Signed-off-by: siddontang <siddontang@gmail.com>

* add titan blob-run-mode

* checkout latest bug fix and titan stats

* move Titan to separate repository
Signed-off-by: Yi Wu <yiwu@pingcap.com>

This is to get around borrow checker for TiKV side of changes. Other APIs also pass in structs as reference.

Adding BlockBasedTableOptions::set_block_cache so we can set shared block cache instance to different column family and different DB instance.

Also adding LRUCacheOptions and Cache structs.

Update RocksDB to include the following changes:
018aa1972 Titan: fix error message formatting (#84)
ee2f17ca8 Fix crash with memtable prefix bloom and key out of prefix extractor domain (#5190)
16ace7c47 Titan: Add snapshot related test (#80)
ee8b59301 Titan: Fix iterator fail to pass SuperVersion to underlying iterator (#79)

Signed-off-by: Yi Wu yiwu@pingcap.com

Signed-off-by: Connor1996 <zbk602423539@gmail.com>

Update .gitmodules to point to pingcap/rocksdb tikv-3.0 branch. Also update rocksdb to include the following changes:

75133b1b6 2019-03-26 yiwu@pingcap.com Fix SstFileReader not able to open ingested file (#5097)
7ca9eb754 2019-03-26 yiwu@pingcap.com Fix BlockBasedTableIterator construction missing index_key_is_full parameter
Signed-off-by: Yi Wu <yiwu@pingcap.com>

We should not rely on a specific version of rust.

We need to support encryption environment created outside.

* Support encrypted env

* Support encrypted env

* Add tests

* guard base env

* guard base env

* guard base env

* *: add wrapper for IOStatsContext

* *: format

* *: test more fields

* *: remove allocate_nanos because darwin doesn't use it

Signed-off-by: zhangjinpeng1987 <zhangjinpeng@pingcap.com>

* rust-toolchain: use a specific version

* submodule: remove shallow

Previous implementation relies on auto compactions to move files to
the specific level, which is not reliable. This PR controls the
compaction manually to make sure the files will be placed at the
expected level.

* set_env for DBOptions
Signed-off-by: zhangjinpeng1987 <zhangjinpeng@pingcap.com>

* impl display for compaction_reason
Signed-off-by: zhangjinpeng1987 <zhangjinpeng@pingcap.com>

* format code
Signed-off-by: zhangjinpeng1987 <zhangjinpeng@pingcap.com>

Some trivial changes are applied:
- Refactor Makefile
- Refactor README.md
- Add the rust-toolchain
- Update RocksDB submodule
- Reorganize the tests structure

* export compaction reason
Signed-off-by: zhangjinpeng1987 <zhangjinpeng@pingcap.com>