EKHARA 3.0: An update of the EKHARA Monte Carlo event generator

The Monte Carlo event generator EKHARA was upgraded during last years. The upgrades presented here contain: (a) the inclusion of new final states $e^+e^-\to e^+e^-\eta$, $e^+e^-\to e^+e^-\eta'$, $e^+e^-\to e^+e^- \chi_{c_i}$, and $e^+e^-\to e^+e^- \chi_{c_i} (\to J/\psi (\to \mu^+\mu^-)\gamma)$; b) new $\gamma^*-\gamma^*-P$ transition form factors and c) the radiative corrections to the reactions $e^+e^-\to e^+e^-P$. For the upgrades (a) and (b), we present here only the pieces missing in other publications, mostly algorithms used in the phase space generation. The radiative corrections are presented here for the first time. A new algorithm of the phase space generation for the reaction $e^+e^-\to e^+e^-P \gamma$ being its main part. A comparison with GGRESRC generator is presented. Big differences between the radiative corrections calculated by the EKHARA and the GGRESRC generators are observed. The previous version of this program (AEIO_v1_0) may be found at http://dx.doi.org/10.1016/j.cpc.2011.01.02