expPanelFun should be a fullpath

[k1o0]

Describe the bug Currently expPanelFun (added by inferParameters) is just the name. If there is a panel of the same name in the path, that one is loaded, instead of the one in the folder of your expDef. Also fileFunction should be used in case the panel isn't on the path:

https://github.com/cortex-lab/Rigbox/blob/cd888f0ae2653ac78651243b22d566ab67a6fb60/%2Beui/ExpPanel.m#L138-L141

Expected behavior Should be a full path to ensure the correct panel class is instantiated.