Refactor .actrc locations and default image survey (#600)

* refactor: move survey/cfgs into own funcs, read XDG base dirs for config

Moved actrc locations to own func since it can be reused.
Moved survey part to own func due to high cyclomatic complexity.
Added XDG config dir to config locations.
Replaced using HOME envvar with go-homedir module since it's already
an indirect dependency and handles home directories better
for each GOOS.

* refactor: use `go-homedir`, check if XDG var is not empty

go.mod

@@ -5,7 +5,6 @@ go 1.16
 require (
 	github.com/AlecAivazis/survey/v2 v2.2.7
 	github.com/Masterminds/semver v1.5.0
-	github.com/MichaelTJones/walk v0.0.0-20161122175330-4748e29d5718 // indirect
 	github.com/andreaskoch/go-fswatch v1.0.0
 	github.com/containerd/containerd v1.4.1 // indirect
 	github.com/containerd/continuity v0.0.0-20200928162600-f2cc35102c2a // indirect
@@ -21,7 +20,7 @@ require (
 	github.com/joho/godotenv v1.3.0
 	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51
 	github.com/kevinburke/ssh_config v0.0.0-20201106050909-4977a11b4351 // indirect
-	github.com/mgutz/str v1.2.0 // indirect
+	github.com/mitchellh/go-homedir v1.1.0
 	github.com/moby/buildkit v0.8.1
 	github.com/moby/sys/mount v0.2.0 // indirect
 	github.com/opencontainers/image-spec v1.0.1
@@ -38,7 +37,6 @@ require (
 	golang.org/x/term v0.0.0-20201117132131-f5c789dd3221
 	google.golang.org/genproto v0.0.0-20201117123952-62d171c70ae1 // indirect
 	google.golang.org/grpc v1.33.2 // indirect
-	gopkg.in/godo.v2 v2.0.9
 	gopkg.in/sourcemap.v1 v1.0.5 // indirect
 	gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776
 	gotest.tools/v3 v3.0.2