* Fix mistake in gitignore file and add in missing core files.

The missing leading slash on "lib" meant all folders names lib in the directory tree are ignored, rather than just the top level PlatformIO lib folder

* Add LiquidCrystal Library and associated headers modified to compile.

Implement AVR Platform

PlatformIO can be used with VSCode.  VSCode creates a .vscode directory which should be ignored.

For compatibility with DevIoT, until that can be solved.

- move platformio.ini out of source directory to be more consistent with 'normal' PlatformIO usage
  - facilitates IDE integration
- add related .gitignores

Also added the new .pio-related directory to .gitignore, and a few ignores for those who use cmake.

Refer to http://git-scm.com/docs/gitignore
to see why this is appropriate

Move the .gitignore out of the Marlin subdirectory so it applies to
the whole tree, and add some missing patterns.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>