amplify-xcode: foundation and import-config command (#950)

* amplify CLI iOS core structure

* tooling and general setup

* import-config command, CLI interface

* docs

* commit xcodeproj files and settings

* resolve home directory in base path, AmplifyEnvironment glob function

* clean AmplifyCommandEnvironment, simplify task execution

* amplifyFileManager abstraction, refactor AmplifyEnvironmentFileManager

* commandEnvironment unit tests

* unit tests CommandImportConfig

* test ImportConfigTasks

* remove currentDirectory property

* remove different types of task executor, add more unit tests

* remove date from copyright headers

* update copyright header

* test CommandEnvironment::contentsOfDirectory

* update inline docs, typealias task successful result

* check for config files

* set multiple targets, separate core from CLI, improve testability

* rename AmplifyCLI -> AmplifyXcode

Author: diegocstn

AmplifyTools/AmplifyXcode/.gitignore

@@ -0,0 +1,7 @@
+.DS_Store
+.build
+/Packages
+AmplifyXcode.xcodeproj/xcuserdata
+AmplifyXcode.xcodeproj/*.plist
+xcuserdata/
+