Cleaning up examples/ models and starter .env files (#1124)

Closes https://github.com/go-skynet/LocalAI/issues/1066 and
https://github.com/go-skynet/LocalAI/issues/1065

Standardizes all `examples/`:
- Models in one place (other than `rwkv`, which was one-offy)
- Env files as `.env.example` with `cp`
    - Also standardizes comments and links docs

examples/models/.gitignore

@@ -0,0 +1,7 @@
+# Ignore everything but predefined models
+*
+!.gitignore
+!completion.tmpl
+!embeddings.yaml
+!gpt4all.tmpl
+!gpt-3.5-turbo.yaml

examples/models/completion.tmpl

@@ -0,0 +1 @@
+{{.Input}}

examples/models/embeddings.yaml

@@ -0,0 +1,6 @@
+name: text-embedding-ada-002
+parameters:
+  model: bert
+threads: 4
+backend: bert-embeddings
+embeddings: true

examples/models/gpt-3.5-turbo.yaml

@@ -0,0 +1,16 @@
+name: gpt-3.5-turbo
+parameters:
+  model: ggml-gpt4all-j
+  top_k: 80
+  temperature: 0.2
+  top_p: 0.7
+context_size: 1024
+stopwords:
+- "HUMAN:"
+- "GPT:"
+roles:
+  user: " "
+  system: " "
+template:
+  completion: completion
+  chat: gpt4all

examples/models/gpt4all.tmpl

@@ -0,0 +1,4 @@
+The prompt below is a question to answer, a task to complete, or a conversation to respond to; decide which and write an appropriate response.
+### Prompt:
+{{.Input}}
+### Response: