Resolve "Provide script for deployment"

Closes #94 (closed)

This MR includes nfsinit script silecs_yocto and 3 scripts for selecting the environment. The silecs_yocto is a modified version of the fesa_yocto taken from /common/export/nfsinit/global. The silecs_yocto is meant to replace fesa_yocto in case of silecs deployments.

The linking is done by the release_yocto.sh, which removes the link created by FESA release and adds the one for silecs. In addition it also copies the snap7 library and releases the silecs param files. Snap7 must be copied this way since the location /common/usr/cscofe/silecs/snap7 can't be mounted from the FEC, so instead the fesa_yocto/silecs_yocto copies all the libraries from the /common/export/fesa/local/<fecname>/<classname>/ to /usr/lib.