Add usage statistics for buttons clicked

Add usage statistic events with the following names when the following buttons are clicked:

• "CreateContentButton" when the user clicks the '+' button but is not linked to a component (there is no component parameter configured)
• "CreateContentButtonWithComponent" when the user clicks the '+' button and the document is added to the component (using a component parameter)
• "PickContentButton" when the user clicks the magnifying glass button to select a document for a component
• "DocumentLocationPicker (create content panel)" when the user clicks the button that opens the document location picker in step 1 of Create Content.
• "CreateContent1Cancel" when the user clicks the 'Cancel' button in step 1 of Create Content.
• "CreateContent1Create" when the user clicks the 'Create' button in step 1 of Create Content and successfully moved to step 2.
• "CreateContent2Cancel" when the user clicks the 'Discard' button in step 2 of Create Content
• "CreateContent2Done" when the user clicks the "Save" button in step 2 of Create Content and successfully moves to the Visual Editor.

For developers: reporting usage statistics from Angular code can be done via 'CmsService.reportUsageStatistic(eventName)'.