Added copyright license for WiFi shield library

See #1117
Merge branch 'master' into ide-1.5.x
Removed useless hidden files
Updated .gitignore
Closes #996
Merge pull request #1902 from arduino/ide-1.5.x-hidden-files-removed

Removed useless hidden files
Merge branch 'ide-1.5.x' into ide-1.5.x-avr-toolchain-gcc-4.8.1