Fix heading offset

[ctzsnooze]

The heading value shown in Explorer's IMU calculation did not match that shown in the GPS Heading or IMU Debug values.

I noted that the blackbox IMU heading calculation is derived from other parameters, and differs from the IMU heading value in debugs. However it may be useful in some cases, and should at least have the same values and display the same when graphed. This PR fixes that problem so that all heading values match up numerically and in graphs.

Other minor changes:

• changed 'deg' to the degree symbol, consistently
• put a space before units, consistently, for clarity
• removed unnecessary whitespace
• added Altitude graph configuration
• added a small change to RTH to graph display values, which can be reversed once debugging of maxAlt is complete.

[blckmn]

AUTOMERGE: (FAIL)

• github identifies PR as mergeable -> FAIL
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• at least one RN: label found -> FAIL
• Tested label found -> FAIL
• assigned to an approver -> PASS
• approver count at least three -> FAIL

[haslinghuis]

Suggested change

	value.toFixed(0);
	return value.toFixed(0);

[ctzsnooze]

Thanks, that was a silly mistake.

[haslinghuis]

Suggested change

	var sysConfig = flightLog.getSysConfig();
	var debugModeName = DEBUG_MODE[sysConfig.debug_mode];
	const sysConfig = flightLog.getSysConfig();
	const debugModeName = DEBUG_MODE[sysConfig.debug_mode];

[ctzsnooze]

This change was from a commit that was accidentally added in this PR by mistake.

It was intended to add the debug name into the text that appears to the right of the graph, but it didn't work, so I've removed that commit.

That removes the need to make this change, but I'll put it into the code I was testing.

Thank you again.

[haslinghuis]

Suggested change

	if (heading > 2* Math.PI)
	heading -= 2* Math.PI;
	if (heading > 2 * Math.PI) {
	heading -= 2 * Math.PI;
	}

[ctzsnooze]

thanks, wasn't sure of the need for the braces

[ctzsnooze]

Thanks very much @haslinghuis for your advice and comments.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

No Coverage information
2.7% Duplication

[github-actions]

Do you want to test this code? Here you have an automated build:
Betaflight-Blackbox-Explorer-Linux
Betaflight-Blackbox-Explorer-macOS
Betaflight-Blackbox-Explorer-Windows
WARNING: It may be unstable and result in corrupted configurations or data loss. Use only for testing!