comfirm msg when add learner

set agg pause status

docs: 3.0.4.2

fix: last(tbname) out of memory issue

Remove taosx, connector, explorer and taoskeeper in cloud tdengine

test:comment  the testcase of tmq

test:comment unit test catalog in cases

fix(cache): sychronize commit, read and write threads with writebatch

fix(cache/read): set none to null instead of skipping column

enh(taosAdapter): support get assignment and seek

fix: tsdb read and append _wstart for tsma 

* docs: update csharp connector status

* docs: fix csharp ws bulk pulling

* docs: clarify database param is optional to websocket dsn

* docs: fix java connector mistake

* fix: a few typos

* fix: many typos

* docs: java connector support subscription over websocket

* fix: update 3.0 connector feature matrix

* docs: fix typos and use 3.1.0 in jdbc driver

* fix: update matrix for schemaless java status

* docs: use latest jdbc version in connect section

fix: last(tag) report error issue

fix(cache/commit): skip batch write if empty

Update 01-faq.md

fix: last query taosd crash issue

Update 01-faq.md

docs: update docs for tdinsight and monitor

fix(cache/loading): skip partial loading tables