Spectrel alpha release

[jcfitzpatrick12]

A collection of GitHub issues that, once resolved, will mean Spectrel is ready for an alpha release.

• (issue-xxx) Improve the CLI design (align with Spectre and/or take inspiration from soapy_power)
• (issue-xxx) Introduce a basic build system (e.g., with CMake)
• (issue-xxx) Introduce a basic test suite (e.g., with CTest)
• (issue-xxx) Properly distribute (e.g., installable with apt-get)
• (issue-xxx) Fix read stream fails at high sample rates
• (issue-193) Improve window support
• (issue-xxx) Improve resource management using the goto cleanup pattern (like here)
• (issue-xxx) Set individual frequency components.
• (issue-xxx) Set individual gain components.
• (issue-xxx) Enable setting the antenna.
• (issue-xxx) Enable setting the channel.
• (issue-xxx) Batch recordings.
• (issue-xxx) Configurable recording formats (including SigMF)
• (issue-xxx) Optionally record I/Q samples.