Feature mofa core113 backport numeric evaluation

Created by: mfauvet

Backport modifications from https://github.com/mensiatech/openvibe/pull/1223:

• Replace evaluateSettingValue function in Kernel with a function checkSettingValue that is in charge to check, while initializing the Player, that settings were correctly set (though it only handles numeric settings for the moment).
• Move the evaluation of settings' step from the getSettingValue() function in kernel to the FSettingValueAutoCast in toolkit: this allows more precision because the result of evaluation doesn't have to be cast into CString as it used to.

Address https://jira.mensia.fr/browse/CORE-113 Tested on: http://jenkins.mensia-ci/job/Certivibe_Linux_Push/45/