Make sIlecs environment setup more resilent

Currently we have just this Silecs Wiki howto which tells on how to add relevant locations into $PATH

Instead, it would be nice to have a script inside /common/usr/cscofe/silecs/$SILECS_VERSION/ to do so. So that only a single file would need to be sourced inside ~/.profile. A silecs version 'latest' or 2 could be used, to always link to the most recent version. Like that users would not need to touch ~/.profile when a new silecs version got released.

Furthermore the silecs environment script could automatically load the FESA environment script, if possible.