[td-98] optimize put performance by comparing the minimum key of skip list before starting to find the appropriated position in the list.

[TD-68] [TD-69] refactor tlog

Feature/2.0tsdb

change the polling timer to 30ms for both read and write queue

Now able to run Python test against local server, without sudo/root privileges

add test script

remove vnodeGetTsdb API

change name style in tsdb

[TD-52] refactor sdb write codes

Feature/2.0tsdb

Add branch coverage support and email-to-author notification.

potential memory leak if no any wal files

[td-98] support projection query on super table