Update issue templates

[kwk]

Added bug and feature request issue templates with https://github.com/fabric8-services/fabric8-wit/issues/templates/edit.

See this blog entry: https://blog.github.com/2018-05-02-issue-template-improvements/

[codecov-io]

Codecov Report

Merging #2091 into master will increase coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2091      +/-   ##
==========================================
+ Coverage   67.45%   67.51%   +0.06%     
==========================================
  Files         158      158              
  Lines       14668    14675       +7     
==========================================
+ Hits         9894     9908      +14     
+ Misses       3820     3815       -5     
+ Partials      954      952       -2

Impacted Files	Coverage Δ
controller/workitem.go	79.74% <0%> (+1.26%)	⬆️
workitem/link/topology.go	88.46% <0%> (+9.51%)	⬆️

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