Disable doclint

Support install by `bin/plugin`, dealing with config files reallocation

For ES 2.3.1

Fixing redundant null check of value known to be non-null.

Fixing the use of inefficient Number Constructor and Double check

Casting math operands before assignment

public static" fields should be constant

- remove double-checked locking

Merging collapsible if statements increases the code's readability.

Replace the usage of System.out or System.err by a logger