Merge pull request #51 from xpc1000/master

DVB: Use the header information to improve the channel switching process.
Update Changelog.
DVB: Get the statistics info from the correct BDA nodes.

Retrieve the signal statistics, i.e. strength and present-flag, from the RF tuner node and quality and lock-flag from the demodulator node to ensure best compatibility with all BDA drivers.

Thanks to robert_s.

This commit fixes #3019.