Revert ""Add library" moved into "Import library" menu"

This reverts commit 1866050e0783e85b814c6afb57fa36318f3496bb.
keep included folder name as top level folder name, delete MAC folder and hidden files
import library also import folder (already expanded libraries)

Conflicts:
	app/src/processing/app/helpers/FileUtils.java
	app/test/processing/app/tools/ZipDeflaterTest.java
"Add library" moved into "Import library" menu
improved import library: complains if invalid zip or folders are selected
also rebuild examples menu after library import
better error message when library names clash
filter out non .ZIP files
Disabled 'fat' (multiplatform) library check.

Conflicts:
	app/src/processing/app/Base.java
removed check on .h file existence
Backported OnlyDirs.class
Fixed disappearing 'Import library' menu
Updated revision log