[Halla12_software] test "solid_gemc" and sub-detector simulation

[Zhiwen Zhao]

Dear All

I have uploaded the code "solid_gemc" into SVN.
It compiles solid hit process routine with GEMC as library into a single 
binary code.

I added sample codes for sub-detector simulation into the SVN also.

The wiki is updated and see more detailed info in "readme" files in SVN
https://hallaweb.jlab.org/wiki/index.php/SoLID_Software_Detector_Simulation

You need to update the GEMC to the latest "devel" version by using "go_gemc"

Let me know any question

Zhiwen