Made funMaps for the templates configurable and hot-reloadable

[tboerger]

Now templates (function maps for helpers) can be better configured and we can keep the reload on request of the templates.

[codecov-io]

Codecov Report

Merging #962 into develop will increase coverage by 0.78%.
The diff coverage is 77.77%.

@@             Coverage Diff             @@
##           develop     #962      +/-   ##
===========================================
+ Coverage    94.96%   95.75%   +0.78%     
===========================================
  Files           16       16              
  Lines         1410     1413       +3     
===========================================
+ Hits          1339     1353      +14     
+ Misses          58       49       -9     
+ Partials        13       11       -2

Impacted Files	Coverage Δ
gin.go	90.64% <77.77%> (+0.64%)	⬆️
context.go	96.27% <0%> (+0.62%)	⬆️
debug.go	82.35% <0%> (+23.52%)	⬆️

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[appleboy]

LGTM

[appleboy]

@tboerger Just add testing.