server: add network stat plugin framework

Enable custom network statistics plugin framework. Use platform
specific custom implementation to compute network stats
and enforce quota for user
Change-Id: Ie711ec0bbd58bf72c2b3450708768a02cfbba2f8

server: modify network stat plugin framework
Add setUpstream function from Tethering to handle IPv6-only
Tethering.
Change-Id: I38392d0678df027c54469564746ee5d9897f5829

frameworks: Avoid calling API if jar loading fails
Even if the ConnectivityExt jar file is not
present, APIs are getting called resulting in page
faults. Avoid calling APIs if ConnectivityExt jar
file is not present or the jar loading fails.
Change-Id: Ie0983c03f8d35aa11cb86e19244b6aac529ac099

server: enhance network stat plugin framework
Add peekTetherStats function for third party apps to query
current hardware statistics.
This API is necessary to allow third party applications to
inquire about hardware statistics without affecting
NetworkStatsService accounting.
Change-Id: I90633585c8af6983f64ac78a77ee0419731a2a44

server: Whitelist non-INTERNET/non-CELLULAR Network for metering
Avoid setting a quota or counting statistics for non-internet
and non-cellular Networks.  Fixes an issue with metering feature
where mobile data usage is incorrectly applied to IMS or other
non-internet PDN.
Change-Id: Ib68f5e560ea1dd230747e4f367081501b70cfc60

Related CRs: 878013 959359 936622 984228 998263 984189
CRs-Fixed: 994082

Change-Id: Ie711ec0bbd58bf72c2b3450708768a02cfbba2f8