add UI backend support

add manager backend(will be used by Nature-Manager-UI)
db:meta add id field
db:relation add id field

0.20.2

Chinese doc: fix architecture.md

0.20.1

• finished English doc and adjust Chinese doc:
  • meta.md
  • executor.md
  • nature-interface.md
  • data-define.md
  • builtin-executor

0.20

• incompatible change: change Instance table design, split ins_key into meta, ins_id and para
• incompatible change: use decimal replace hexadecimal to represent the instance.id
• remove u128 support
• incompatible change: KeyCondition.id type changed to u64 from String
• incompatible change: move need_all, need_any, need_none from TargetState to FlowSelector
• incompatible change: merge TargetState to RelationTarget
• incompatible change: context_name to dynamic_para
• simplify the readme(CH && EN)
• bug fix: if target last instance check failed, should return environment error

0.19

• make ConverterReturned to fit for json communication
• simple readme.md(CH)
• add Executor.md(CH)
• add nature-interface.md(CH)

0.18

release.zip

• incompatible change: task_id from char to bigint
• incompatible change: filter_before -> convert_before
• incompatible change: filter_after -> convert_after

0.17

• change input method return type from u64 to hex string
• change crate fern to env_logger
• optimize input interface performance

0.16

• merge nature, common, db and retry projects together
• merge demo, demo-common, demo-executor, demo-executor-restful together.

0.15

• id64 support: use u64 as generated id
• user can custom log level
• optimize: normalize meta property for inputted instances
• optimize: message for the database when it is unready
• bug: generated state-instance create_time does not set

0.14.1

• rename MetaSetting.output_last to MetaSetting.only_one and fix bug around
• optimize: builtin-task_checker include update time check