Refactor agents and tools (#91)

* Move tools to agents

* Move agents to dedicate place

* Remove subclassing BaseAgent from BaseTool

knowledgehub/agents/react/prompt.py

@@ -0,0 +1,28 @@
+# flake8: noqa
+
+from kotaemon.llms import PromptTemplate
+
+zero_shot_react_prompt = PromptTemplate(
+    template="""Answer the following questions as best you can. You have access to the following tools:
+{tool_description}
+Use the following format:
+
+Question: the input question you must answer
+Thought: you should always think about what to do
+
+Action: the action to take, should be one of [{tool_names}]
+
+Action Input: the input to the action
+
+Observation: the result of the action
+
+... (this Thought/Action/Action Input/Observation can repeat N times)
+#Thought: I now know the final answer
+Final Answer: the final answer to the original input question
+
+Begin! After each Action Input.
+
+Question: {instruction}
+Thought:{agent_scratchpad}
+    """
+)