Context History Improvements

[rcosta358]

This PR makes some changes to the context history to improve the autocomplete in the extension:

• Saves ghosts/states by file to only suggest ghosts in the current class
• Use annotation position as starting position for method scope so parameters can be suggested in method and parameter refinements
• Introduce boolean variable to know whether a refined variable is a parameter or not so we can bypass the condition that filters variables that are declared after the current position