first stage of the ramping procedure refactoring. Redesigned the procedure of ramping, also the threshold management and the pause process when there is a switch off of the involved attribute.

git-svn-id: https://svn.code.sf.net/p/tango-ds/code/DeviceClasses/AcceleratorComponents/LinacAlba/trunk@18801 3b39871e-fe4b-0410-b5db-e82997f68959
add the ramping feature to the electron gun high voltage.

git-svn-id: https://svn.code.sf.net/p/tango-ds/code/DeviceClasses/AcceleratorComponents/LinacAlba/trunk@18802 3b39871e-fe4b-0410-b5db-e82997f68959