Explorer Integration

Hi,

please let me know if you want me to change something. This pull request contains the integration of the Explorer-1 chips for the ALICE ITS Upgrade. The readout is done using the RD51 SRS.

In addition to the integration, I remove some unnecessary execute rights from files. Furthermore, I've added an option to compile the main library with ROOT in order to make the root and our special tree converter working.

Cheers,
Felix