Bump version to 5.6.1

Remove make_new_version.sh

Summary:
Seems the only function of the script is to create a new branch, which can be done easily. I'm removing it.
Closes https://github.com/facebook/rocksdb/pull/2623

Differential Revision: D5468681

Pulled By: yiwu-arbug

fbshipit-source-id: 87dea5ecc4c85e06941ccbc36993f7f589063878

Make TARGETS file portable

Summary:
Instead of hard coding the path of the internal repo.
Make TARGETS file work anywhere in fbcode
Closes https://github.com/facebook/rocksdb/pull/2586

Differential Revision: D5428122

Pulled By: IslamAbdelRahman

fbshipit-source-id: 21adec82bfbff14ea93532bee789b5f5bbee5b01

Remove arcanist_util directory

Update java/rocksjni.pom

Summary: Closes https://github.com/facebook/rocksdb/pull/2610

Differential Revision: D5445705

Pulled By: siying

fbshipit-source-id: d5f97ffdf5bc18b853c3a106755aca96a650e428

Remove some left-over BSD headers

Summary: Closes https://github.com/facebook/rocksdb/pull/2608

Differential Revision: D5444797

Pulled By: siying

fbshipit-source-id: 690581d03f37822e059a16085088e8e2d8a45016

Add back the LevelDB license file

Summary: Closes https://github.com/facebook/rocksdb/pull/2591

Differential Revision: D5432696

Pulled By: siying

fbshipit-source-id: a613230ab916de0b279a65ef429ede65460a8db2

Remove the licensing description in CONTRIBUTING.md

Summary: Closes https://github.com/facebook/rocksdb/pull/2590

Differential Revision: D5432539

Pulled By: siying

fbshipit-source-id: 49902453bba3c95c1fb8354441b2198649e52bf4

Change RocksDB License

Summary: Closes https://github.com/facebook/rocksdb/pull/2589

Differential Revision: D5431502

Pulled By: siying

fbshipit-source-id: 8ebf8c87883daa9daa54b2303d11ce01ab1f6f75

Fix column_family_test with LITE build

Summary:
Fix column_family_test with LITE build. I need this patch to fix 5.6 branch.
Closes https://github.com/facebook/rocksdb/pull/2597

Differential Revision: D5437171

Pulled By: yiwu-arbug

fbshipit-source-id: 88b9dc5925a6b47af10c1b41bc5b07c4251a84b5