Fix .desktop file according to freedesktop spec
Merge pull request #154 from oxapentane/fix-desktop-file

Fix .desktop file according to freedesktop spec
Only connect I/Q sink if we are recording.
Improve audio recorder robustness.

This patch improives the robustness while recording audio and
performing various operations, such as switching demodualtors
off.
Use shorter I/Q file names.
Functional I/Q recorder.
New I/Q player (WIP)
Restore manual gain settings when HW AGC is diabled.

Fixes one part of issue #141.
Note that gqrx does actually restore AGC, but for some reason the
device ends up having a wrong gain setting.
Fix invalid rtlsdr sample rate selection in I/O config.
Connect new remote freq signal to CFreqCtrl.

This fixes an issue where the frequency controller display didn't
update on certain remote frequency requests.
Make I/Q player child of mainwindow.

This ensures clean and complete exit also while the I/Q player window is open.
Disable DSP while switching between HW and I/Q sources.
Don't reset sample rate in iq_tool.