XWIKI-10307: Add the ability to change the panel columns' width.

...ration-ui/src/main/resources/XWiki/AdminElementsSheet.xml

...i-platform-colibri/src/main/resources/colibri/colibri.css

...ki-platform-flamingo/src/main/resources/flamingo/admin.vm

...form-flamingo/src/main/resources/flamingo/applications.vm

...iki-platform-flamingo/src/main/resources/flamingo/edit.vm

...atform-flamingo/src/main/resources/flamingo/editinline.vm

...atform-flamingo/src/main/resources/flamingo/editpanels.vm

...-platform-flamingo/src/main/resources/flamingo/endpage.vm

...atform-flamingo/src/main/resources/flamingo/htmlheader.vm

...m-flamingo/src/main/resources/flamingo/layoutExtraVars.vm

...atform-flamingo/src/main/resources/flamingo/leftpanels.vm

...o/src/main/resources/flamingo/less/application-panel.less

...orm-flamingo/src/main/resources/flamingo/less/layout.less

...form-flamingo/src/main/resources/flamingo/less/style.less

...tform-flamingo/src/main/resources/flamingo/rightpanels.vm

...platform-flamingo/src/main/resources/flamingo/rightsUI.vm

...latform-flamingo/src/main/resources/flamingo/startpage.vm

...tform-flamingo/src/main/resources/flamingo/stylesheets.vm

...iki-platform-flamingo/src/main/resources/flamingo/view.vm

...ternal/mandatory/XWikiPreferencesDocumentInitializer.java