Improve Add Workbook Horizon UX

Show table with all created workbooks (currently stored in memory
stub), add 'Add Workbook', 'Edit Workbook' and 'Delete Workbook'
actions. Creating/ editing workbook is implemented as modal form (with
Workbook Builder inside).

Change-Id: I26139f674f7c7f3df2d45a0cd714e53b1d28538c