rtl_433_stats v2.2.0

This release is a minor upgrade to v2.1 to support processing records with ISO and Unix Epoch timestamps in JSON log files.

What's Changed

• Update README.md by @hdtodd in #4
• Create v2.2.0 to accept both ISO and Unix Epoch times in the JSON log by @hdtodd in #5

Full Changelog: v2.1.0...v2.2.0

Streamlined file handling

This update features primarily improved input file handling in the Python version, including wildcard and compressed-file handling. It also adds options that can remove extraneous information from reports, making them easier to understand.

The program now prints alerts for individual devices if it sees a change in "battery_ok" or "status" while processing log-file packets from that device.

Two file-extraction Python scripts have been included under the tools directory.

The C version remains unchanged from v1.0.

`rtl_433_stats` v 2.0.0 (renaming from `rtl_snr` v2.0.0

This first release of rtl_433_stats is numbered v2.0.0 to be consistent with the versioning of rtl_snr from which it was developed.

Simplify epoch time calculation

Simplify datetime calculation for ISO format with/without fraction

Minor bug fix and additional information reported

• Fix Python JSON load exception handling to be more explanatory
• Add total and device packet counts
• Use standardized language for "transmissions" and "packets"

Bug fixes and added functionality

This release is essentially a bug-fix release, but with some minor changes and one addition:

• The device descriptor creation step in the Python code now uses just the "model" field if the "id" field is not present in the JSON record: the earlier version failed when that field was not found.
• The REAME has been updated to note that the Python code fails with a "JSON load error" on large files (>600K records). The C code successfully processes those large files.
• SNR-ITGT has been added to the Python directory to provide both signal-to-noise statistical analysis and Inter-Transmission Gap Time analysis. The lTGT is the time-gap between successive transmissions from the same device. SNR-ITGT performs the same statistical analysis on ITGT as it does on SNR and reports them together. The ITGT report may be less useful for JSON logs with many spurious devices, as the gap time means and standard deviations aren't particularly meaningful. But the report may be useful for analyzing characteristics of devices that routinely and reliably transmit sensor data in your proximity.
• The Python and C code have been separated into to sub-directories for easier maintenance.

Full Changelog: https://github.com/hdtodd/rtl_snr/commits/v1.2.0