Updated docs, cleaned things up, DRY's up function format stuff. (#688)

* Updated docs, cleaned things up, DRY's up function format stuff.

* deleted files

* updated bad link

docs/developers/function-file.md

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+# Function files
+
+Functions files are used to assist fn to help you when creating functions.
+
+An example of a function file:
+
+```yaml
+name: fnproject/hello
+version: 0.0.1
+type: sync
+memory: 128
+config:
+  key: value
+  key2: value2
+  keyN: valueN
+headers:
+  Content-Type: text/plain
+build:
+- make
+- make test
+expects:
+  config:
+    - name: SECRET_1
+      required: true
+    - name: SECRET_2
+      required: false
+```
+
+`name` is the name and tag to which this function will be pushed to and the
+route updated to use it.
+
+`path` (optional) allows you to overwrite the calculated route from the path
+position. You may use it to override the calculated route. If you plan to use
+`fn test --remote=""`, this is mandatory.
+
+`version` represents current version of the function. When deploying, it is
+appended to the image as a tag.
+
+`runtime` represents programming language runtime, for example,
+'go', 'python', 'java', etc.  The runtime 'docker' will use the existing Dockerfile if one exists.
+
+`build` (optional) is an array of local shell calls which are used to help
+building the function. TODO: Deprecate this?
+
+`type` (optional) allows you to set the type of the route. `sync`, for functions
+whose response are sent back to the requester; or `async`, for functions that
+are started and return a call ID to customer while it executes in background.
+Default: `sync`.
+
+`memory` (optional) allows you to set a maximum memory threshold for this
+function. If this function exceeds this limit during execution, it is stopped
+and error message is logged. Default: `128`.
+
+`cpus` (optional) is the amount of available CPU cores for this function. For example, `100m` or `0.1`
+ +will allow the function to consume at most 1/10 of a CPU core on the running machine. It
+ +expects to be a string in MilliCPUs format ('100m') or floating-point number ('0.5').
+ +Default: unlimited.
+
+`timeout` (optional) is the maximum time a function will be allowed to run. Default is 30 seconds. 
+
+`headers` (optional) is a set of HTTP headers to be returned in the response of
+this function calls.
+
+`config` (optional) is a set of configuration variables to be passed onto the function as environment variables.
+These configuration options shall override application configuration during functions execution. See [Configuration](configs.md)
+for more information.
+
+`expects` (optional) a list of config/env vars that are required to run this function. These vars will be used when running/testing locally,
+if found in your local environment. If these vars are not found, local testing will fail.
+
+## Hot functions
+
+hot functions support also adds two extra options to this configuration file.
+
+`format` (optional) is one of the streaming formats covered at [function-format.md](function-format.md).
+
+`idle_timeout` (optional) is the time in seconds a container will remain alive without receiving any new requests; 
+hot functions will stay alive as long as they receive a request in this interval. Default: `30`.