Fix connectivity phase metrics and averaging

[Moo-Marc]

• Fix WPLI and ciPLV which both had errors in the formulae.
• Refactor code for coherence and phase metrics (plv, ciplv, wpli), in large part to allow proper averaging of terms across files, before the final connectivity formula is "assembled". Previously, only spectral coherence did it properly, now also hilbert/morlet coherence and all phase metrics.
• Extended time-frequency options for phase metrics
• Added full time resolution for coherence (when estimating across trials)
• GUI: Moved time-resolved coherence from "envelope correlation" process back to coherence
• Harmonized GUI between all PLV, coherence, envelope correlation processes
• Removed pre-2019 coherence processes from deprecated folder, moved 2021 versions there, 3 new process files
• Major performance improvements.
• Confirmed plv and coherence on single file gives exact same results as previously
• Fixed bugs in envelope correlation (AxB error, values > 1)

Remaining:

• Additional testing, esp. other connectivity processes
• envelope correlation: similar averaging issue due to abs at file level, other issues
• ~10 "TODO" left in code

[Moo-Marc]

I committed one fix and minor comment tweaks not mentioned here.