Improve documentation

Improve wording consistency, fix types, add more information about
default value, ...

Following component were reworked during this batch:

* AbstractItemViewHeader.qml
* Action.qml
* ActionTextField.qml
* ActionToolBar.qml
* ApplicationItem.qml
* ApplicationWindow.qml
* Avatar.qml
* BasicListItem.qml
* Card.qml
* CardsGridView.qml
* CardsLayout.qml
3 jobs for work/doc-i in 48 seconds (queued for 5 seconds)
Status Name Job ID Coverage
  Build
passed android_qt515 #145795
Linux

00:00:19

passed freebsd_qt515 #145796
FreeBSD

00:00:41

passed suse_tumbleweed_qt515 #145794
Linux

00:00:48