Docs refactor (#480)

Big docs refactor! Motivation is to make it easier for people to find
resources they are looking for. To accomplish this, there are now three
main sections:

- Getting Started: steps for getting started, walking through most core
functionality
- Modules: these are different modules of functionality that langchain
provides. Each part here has a "getting started", "how to", "key
concepts" and "reference" section (except in a few select cases where it
didnt easily fit).
- Use Cases: this is to separate use cases (like summarization, question
answering, evaluation, etc) from the modules, and provide a different
entry point to the code base.

There is also a full reference section, as well as extra resources
(glossary, gallery, etc)

Co-authored-by: Shreya Rajpal <ShreyaR@users.noreply.github.com>

docs/reference/modules/agents.rst

@@ -1,4 +1,4 @@
-:mod:`langchain.agents`
+Agents
 ===============================
 
 .. automodule:: langchain.agents

docs/reference/modules/chains.rst

@@ -1,4 +1,4 @@
-:mod:`langchain.chains`
+Chains
 =======================
 
 .. automodule:: langchain.chains

docs/reference/modules/docstore.rst

@@ -1,4 +1,4 @@
-:mod:`langchain.docstore`
+Docstore
 =============================
 
 .. automodule:: langchain.docstore

docs/reference/modules/embeddings.rst

@@ -1,4 +1,4 @@
-:mod:`langchain.embeddings`
+Embeddings
 ===========================
 
 .. automodule:: langchain.embeddings

docs/reference/modules/example_selector.rst

@@ -1,4 +1,4 @@
-:mod:`langchain.prompts.example_selector`
+Example Selector
 =========================================
 
 .. automodule:: langchain.prompts.example_selector

docs/reference/modules/llms.rst

@@ -1,6 +1,7 @@
-:mod:`langchain.llms`
+LLMs
 =======================
 
 .. automodule:: langchain.llms
    :members:
+   :inherited-members:
    :special-members: __call__

docs/reference/modules/prompt.rst

@@ -1,4 +1,4 @@
-:mod:`langchain.prompts`
+PromptTemplates
 ========================
 
 .. automodule:: langchain.prompts

docs/reference/modules/python.rst

@@ -1,4 +1,4 @@
-:mod:`langchain.python`
+Python REPL
 =============================
 
 .. automodule:: langchain.python

docs/reference/modules/serpapi.rst

@@ -1,4 +1,4 @@
-:mod:`langchain.serpapi`
+SerpAPI
 =============================
 
 .. automodule:: langchain.serpapi

docs/reference/modules/text_splitter.rst

@@ -1,4 +1,4 @@
-:mod:`langchain.text_splitter`
+Text Splitter
 ==============================
 
 .. automodule:: langchain.text_splitter

docs/reference/modules/vectorstore.rst

@@ -1,4 +1,4 @@
-:mod:`langchain.vectorstores`
+VectorStores
 =============================
 
 .. automodule:: langchain.vectorstores