Implement repeat mode for I/Q replay tool

[reald]

The "Device string" in "Complex Sampled (IQ) File" Source is a bit uncomfortable. If you want to replay a .sigmf file the I/Q replay tool is more comfortable because it selects the sample rate for you (but not the core:frequency?).

But a disadvantage is the lack of the repeat mode like the "Complex Sampled (IQ) File" Source has.

=> Implement a repeat mode for IQ replay tool

[vladisslav2011]

Duplicate of #1098
Possible fix: #1108
Feel free to test it and leave some feedback.