A first working version of DDR support

This commit adds support for using an RTL2832U DVB-T dongle as a
receiver. It is a rather hackish implementation for now and only one
DDR can be set up. Also the tuner parameters, like frequency and
frequency correction, is hardcoded.
There now is a cpp file for class WbRxRtlTcp
Renamed WbRxRtlTcp back to RtlTcp
Now possible to configure the WBRX in the config file
Fixed some serious bugs
Improved channel filtering
Gain setting improvements

* Now possible to specify negative gain

* Gain is now given in dB nstead of in 10th of dB:s in the config file.
Changed the Translator to use a lookup table
Made a small vector preallocation improvement
Signal level detectors are now created using a factory
Implemented a DDR pre-demod signal level detector
Now demodulating down to 16kHz sampling frequency

The decimation now look like:

  960kHz -> 192kHz -> 32kHz -> demodulation -> 16kHz

The end result is a 6500Hz wide audio channel.
The RtlTcp class now know tuner type names
Implemented tuner center frequency autotuning
Fixed a bug in the Translator
Implemented a distorsion detector for RtlTcp
Handle DDR:s that fall outside the tuner bandwidth

DDR:s that fall outside of the tuner bandwidth will not be disabled and
a warning is printed.

Fixed a delete-bug which caused a segfault when quitting. Now cleaning
up the WbRxRtlTcp object properly.
Improved/bugfixed the autotune feature
RtlTcp now reconnect if disconnected
Increased audio gain