Review changes for HTTP paths

This reviews the code and fixes up suggestions made by team for
the HTTP paths PR #789.

- Removed feature-flag (this is backwards-compatible, so I see
no value in adding the flag)
- There was a URL transform happening for calls proxied to the
back end, I changed this for the nil-transform - i.e. it does not
change anything in the URL
- Introduced variables to describe the regex indicies used in
the URL trimming.

Tested with Docker Swarm with a ruby-microservice, with
system calls and with function calls using the UI.

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

gateway/types/readconfig.go

@@ -105,8 +105,6 @@ func (ReadConfig) Read(hasEnv HasEnv) GatewayConfig {
 	cfg.DirectFunctions = parseBoolValue(hasEnv.Getenv("direct_functions"))
 	cfg.DirectFunctionsSuffix = hasEnv.Getenv("direct_functions_suffix")
 
-	cfg.PassURLPathsToFunctions = parseBoolValue(hasEnv.Getenv("pass_url_path_to_functions"))
-
 	cfg.UseBasicAuth = parseBoolValue(hasEnv.Getenv("basic_auth"))
 
 	secretPath := hasEnv.Getenv("secret_mount_path")
@@ -152,10 +150,6 @@ type GatewayConfig struct {
 	// If set this will be used to resolve functions directly
 	DirectFunctionsSuffix string
 
-	// If set to true, the requested path will be passed along to the function, minus the "/function/xyz"
-	// prefix, else the path will be truncated to "/" regardless of what the client sends.
-	PassURLPathsToFunctions bool
-
 	// If set, reads secrets from file-system for enabling basic auth.
 	UseBasicAuth bool