update model.md

Docs/update latest feature

Update docs.md

Update docs.md

Update insert.md

[TD-4473] update alter keep test

Test/td 4526

test session on second timestamp fields

Update docs.md

Update getting-started.md

update evaluation.md

[TD-4669] <docs>: upload English documents & pictures for version 2.0.

[td-4673]<fix>: fix bug in derivative.

[TD-3963]alter db rpc return when vnode response

[TD-4669] <docs>: upload English documents for version 2.0.

[TD-4043]<test>add some scenarios for session window

[TD-4602]<test>: add test case: diff function for super table

Test/td 4658

Feature/m2d