Implement basic app.ini and path checks to doctor cmd (#10064)

* Add doctor check of app.ini paths

* Make /custom dir not mandatory

* Fix message and improve interface

* Update cmd/doctor.go

Co-Authored-By: John Olheiser <42128690+jolheiser@users.noreply.github.com>

* Apaise lint

* Isn't the linter a sweet? (1)

* Isn't the linter a sweet? (2)

* Isn't the linter a sweet?? (3)

* Restart CI

Co-authored-by: John Olheiser <42128690+jolheiser@users.noreply.github.com>
Co-authored-by: zeripath <art27@cantab.net>

modules/options/static.go

@@ -112,3 +112,8 @@ func fileFromDir(name string) ([]byte, error) {
 
 	return ioutil.ReadAll(f)
 }
+
+// IsDynamic will return false when using embedded data (-tags bindata)
+func IsDynamic() bool {
+	return false
+}