detectEcgWithAngle(​ecg, fSInHz, varargin): Heartbeat detection using sample-to-sample angle

[!!!] Detection results may have changed for sampling rates ~= 200 Hz.
[FIX] Reintroduced the DESIGNFILT call for sampling rates ~= 200 Hz to get the filter coefficient right.
[FIX] Crash when plotting detection results with only 1 peak.

[FIX] Crash when plotting empty detection results.
[FIX] Crash when plotting data with all-normal rr intervals.
[ADD] New optional input 'minTStartInSec' to remove erroneous detections at the start of the recording.

Forgot to mention another modification:
[MOD] The transfer function representation of the bandpass-filter is now to avoid calling the slow DESIGNFILT method every time. This also removes the according dependency.

[FIX] Checks for optional dependencies now work properly.