Better doc comment for User.context()

Update changelog for 2.5.0

Update changelog for 2.4.3

Update changelog for 2.4.2

Update changelog for 2.4.1

Merge pull request locustio#1888 from locustio/fix-issue-with-custom-…

…arguments-in-file-when-not-running-headless

Fix issue with custom arguments in config file when not running headless

Merge pull request locustio#1871 from locustio/disable-setting-custom…

…-parameters-of-None-or-boolean-type-in-web-ui

Disable setting custom parameters of None or boolean type in web UI. Fixes locustio#1870