add tests for qp solvers
add tests for qp solvers

jerkos/cobrapy,aebrahim/cobrapy,JuBra/cobrapy,jeicher/cobrapy,aebrahim/cobrapy,JuBra/cobrapy,zakandrewking/cobrapy,zakandrewking/cobrapy,jeicher/cobrapy,jerkos/cobrapy