Improve variable names in strategy implementations

Renamed many of the variables and method parameters
in the strategy implementations to make the names
more meaningful.  Also changed the abstract method
signature in base.py to reflect these changes.

Closes-Bug: #1541615

Change-Id: Ibeba6c6ef6d5b70482930f387b05d5d650812355

watcher/decision_engine/strategy/strategies/base.py

@@ -64,10 +64,10 @@ class BaseStrategy(object):
         self._osc = osc
 
     @abc.abstractmethod
-    def execute(self, model):
+    def execute(self, original_model):
         """Execute a strategy
 
-        :param model: The name of the strategy to execute (loaded dynamically)
+        :param original_model: The model the strategy is executed on
         :type model: str
         :return: A computed solution (via a placement algorithm)
         :rtype: :class:`watcher.decision_engine.solution.base.BaseSolution`