Move to libbase properties

The libcutils interface cannot read properties with value length > 92
characters, whereas the libbase one can.  ro.build.fingerprint may be
larger than this size in the future, so we move to libbase to prepare.

Bug: 23102347
Bug: 34954705
Test: unit tests
Change-Id: Idca886021bdd71623052a452faf582532725ffdc