JqlQuery addExpression method must accept JqlFunction in value param

[lotimopa]

Problem

If i use JqlFunction in expression like for exemple ->addExpression('duedate', '<=', JqlFunction::endOfMonth())
an error has occured cause param value do not accept JqlFunction

Proposed Solution

In JqlQuery addExpression method, add possibility to pass JqlFunction for value param
because value is treated by quote value self::quote($value) and quote method accept JqlFunction

[lotimopa]

#105