Place build related files in a .build sub-directory

[woolseyj]

Enhancement Request

Current Behavior

The various build related files, e.g. *.elf, *.hex, and sketch.json, can clutter up a sketch workspace directory.

Requested Behavior

I suggest these types of files be placed in a hidden .build sub-directory that can be more easily ignored by users and tools such as Git.

[cmaglie]

This has been fixed in #687.
Eventually we decided to place the builds inside the build folder (without the . dot).

[woolseyj]

Thank you.