* [PASS] Improve loop partition to remove un-necessary warning.

* fix comment

* [SCHEDULE]enable partition const loop with build flag (#719)

    * enable partition loop with build flag

    * add a testcase, and modify LoopPartition related cases

*     * add document for split_const_loop

* [RUNTIME] Add System Lib

* lint

* lint

* fix compile

* Add CombineInternal<Mod> & Fix LoopPartition

* Add check for path

* [PASS] Use likely tag & enable LoopPartition by default

* [PASS] Support thread_axis partition

* Take IfThenElse branch method

* [PASS] Insert branch at the innermost thread scope

* [PASS] Select candidates before trying to partition & add test for select

* [PASS] Clean code

* Fix

* Remove print & assert vectorize happens

* [PASS] Support for partition loops with thread_axis

* Add check for AttrStmt.attr_key

* [IterVar/REFACTOR] Add types to IterVar

* [ARITH/REFACTOR] Move IntSet to include

* [REFACTOR/OP] Move Op detail to seperate folder.

* fix test

* loop_partition draft

* divide loop variable into constant domain and variable domain & consider multiple partitions

* process doubt interval

* fix and refactor, add relax_map arg in BoundDeduce

* fix testcase and comment

* rebase to zero, convert to SSA

* change the logic of generating loop code & fix issues

* add a testcase for relax map in deducebound && fix issues

* clean code

* const auto&

* add test_multi_if