[SQUASH] Address PR comments.

* Split Parameter into IntParameter/FloatParameter/CategoricalParameter.
* Rename IHyperStrategy to HyperStrategyMixin and use it as mixin.
* --hyperopt parameter is now optional if strategy uses HyperStrategyMixin.
* Use OperationalException() instead of asserts.

freqtrade/optimize/hyperopt_interface.py

@@ -5,15 +5,14 @@ This module defines the interface to apply for hyperopt
 import logging
 import math
 from abc import ABC
-from typing import Any, Callable, Dict, List
+from typing import Any, Callable, Dict, List, Union
 
 from skopt.space import Categorical, Dimension, Integer, Real
 
 from freqtrade.exceptions import OperationalException
 from freqtrade.exchange import timeframe_to_minutes
 from freqtrade.misc import round_dict
-from freqtrade.strategy import IStrategy
-
+from freqtrade.strategy import IStrategy, HyperStrategyMixin
 
 logger = logging.getLogger(__name__)
 
@@ -35,7 +34,7 @@ class IHyperOpt(ABC):
     """
     ticker_interval: str  # DEPRECATED
     timeframe: str
-    strategy: IStrategy
+    strategy: Union[IStrategy, HyperStrategyMixin]
 
     def __init__(self, config: dict) -> None:
         self.config = config