Panels bootstrap layouts 7.x-3.0+12-dev version is better

Hello,

Varbase 7.x-3.4 uses the stable version of Panels bootstrap layouts which is for now 7.x-3.0 but the older versions of varbase were using 7.x-3.0+12-dev which has a lot of features in configuring the bootstrap columns and it's stable as well.

I think we should use the 7.x-3.0+12-dev of the module until it's merged to the stable version.