persist: add the default numbers property array and random number generation

This adds the default numbers property array if it does not exist during
loading. This also adds the function reusing the function generating random key
to generate random number for the first time when the local device's properties
are created.

Unittest PersistTestSuite is added, and its tests include
- LocalDeviceNameGetterAndSetter
- LocalDiscoveryGetterAndSetter
- DeviceGetAddDel
- DeviceKeyAddGetDel
- DeviceNumerAddGetDel

BUG=chromium:805112
TEST=build and run unittest by "./new_blue_unittest
     --gtest_filter=*PersistTestSuite*"

Change-Id: Ic038c997d3e7f43df1af9a3c0284a0b46d814bf6
7 files changed