Draft: Add jenkins support

MR adds Jenkins support for x86_64 and yocto targets. It contains Jenkinsfile and minor changes to shell scripts used for installation purposes:

• Standardize build directories names to build-{TARGET} instead of build (x86_64 target) and build-yocto (yocto target)
• Start setting GSI_SILECS_PATH from environmental variable (CMake was already ready for this but option was not used). Note that despite name suggestion this variable is used to include modbus and snap7 libraries.

Link to Jenkins project: https://builder.acc.gsi.de/jenkins/job/acofec/job/silecs/job/silecs-test/