Merge the lecturers and participants templates

[krzys-h]

This ensures that columns such as "Previous editions" are available in both views and reduces code duplication

Closes #612

To be merged after #623

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This change is 

[codecov[bot]]

Codecov Report

Merging #624 (dcd7fd0) into count-managers (a3027f9) will decrease coverage by 0.04%. The diff coverage is 100.00%.

@@                Coverage Diff                 @@
##           count-managers     #624      +/-   ##
==================================================
- Coverage           84.78%   84.73%   -0.05%     
==================================================
  Files                  15       15              
  Lines                2452     2431      -21     
==================================================
- Hits                 2079     2060      -19     
+ Misses                373      371       -2     

Impacted Files	Coverage Δ
wwwapp/views.py	80.48% <100.00%> (-0.29%)	:arrow_down:

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