Update changelog for changes in release branch

[mdickinson]

Brings the changelog updates from the release/4.7.x branch into master.

[codecov-io]

Codecov Report

Merging #153 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #153      +/-   ##
==========================================
+ Coverage   39.54%   39.59%   +0.04%     
==========================================
  Files         155      155              
  Lines        4592     4592              
  Branches      519      519              
==========================================
+ Hits         1816     1818       +2     
+ Misses       2735     2734       -1     
+ Partials       41       40       -1

Impacted Files	Coverage Δ
envisage/composite_plugin_manager.py	86.66% <0%> (+2.66%)	⬆️

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