Introduce a new birthmark, verbs of methods

[tamada]

Implements a new birthmark, the verb list of the method names.

Ideally, we obtain the verbs of method names from the method codes, such as the following paper.
However, implementing the following algorithm is a hard task, and the efficiency is not known.
Therefore, as the rush work, this implementation obtains the verbs of methods from the plain method names.

• Yosuke Isobe, and Haruaki Tamada, ''Design and Evaluation of the De-obfuscation Method against the Identifier Renaming Methods'', International Journal of Networked and Distributed Computing, Vol. 6, Issue 4, pp. 232--238, September 2018.