Add new methods

Add new methods

1. Change ConnectionProfile.State --> ConnectionProfile.GetState(AddressFamily family)
2. Add PrefixLength to IAddressInformation
3. Add DnsConfigType to IAddressInformation
4. Add GetStatistics() and ResetStatistics() to ConnectionManager
5. Add Refresh() to ConnectionProfile
6. Add PdnType and RoamPdnType to CellularProfile
7. Add GetAllIPv6Addresses() to ConnectionManager

Change-Id: I99b67847b8b508aff8352cb8f0f5f6cce9e37326
Signed-off-by: cheoleun <chleun.moon@samsung.com>