ISIS-537 Add Bootstrap overrides CSS file for Sandstone theme to fix the rendering of the input-group-addon for the dates

https://trello.com/c/6oCefJvi/99-sandstone-theme-date-hint-is-too-large
ISIS-537 Show/hide the CopyLink modal window with alt+] keyboard combination

https://trello.com/c/ZothDcdD/102-bug-if-do-alt-twice-in-succession-then-cancel-does-not-remove-the-veil
ISIS-537 Fix JavaScript for org.apache.isis.viewer.wicket.ui.components.widgets.cssmenu.AjaxDeferredBehaviour.OpenUrlStrategy#NEW_WINDOW. It should be wrapped in a function.

https://trello.com/c/UYl51kIt/101-todoitem-opensourcecodeongithub-a-no-arg-action-returning-a-java-net-url-does-nothing
ISIS-537 Show/Hide the copy link only when hovering the entity's icon and title
ISIS-537 Improve the logic for showing/hiding the CopyLink modal window with alt+] keyboard combination
ISIS-537 Use CSS 'visibility' for showing/hiding the copy link for better IE support
Revert "ISIS-537, ISIS-911 - Remove the extra "Clear" button for Blob/Clob scalars in edit mode"

This reverts commit f605fba1ec596fa79ad9bf63a209114775bf858f.

https://trello.com/c/3ar0leq2/103-my-mistake-we-now-don-t-have-any-way-to-clear-an-attachment-or-blob-if-optional-eg-in-the-todoapp
ISIS-537 Remove margin-bottom: 15px; for .form-group

https://trello.com/c/ATmCqVEy/104-too-much-vertical-space-between-fields-all-themes
ISIS-537 Reduce event more the vertical space between the entity properties by copmletely hiding the label when .label-none.

Remove the top padding (5px) and make the bottom padding 2px bigger (to 7px).

https://trello.com/c/ZaacXqga/105-if-labelat-none-then-remove-the-large-amount-of-vertical-white-space-where-the-label-would-ve-been
ISIS-537 Add 4px padding at the bottom of the label when .label-top

https://trello.com/c/g3Qj4xcE/106-if-labelat-top-add-a-bit-more-vertical-space-between-label-and-field
ISIS-537 Use same space on the left and the right of the form components in the forms (EntityPropertiesPanel and ActionParametersFormPanel)

https://trello.com/c/qCb7H75g/108-left-and-right-margins-in-action-prompt-different
ISIS-537 Disable the resizing of textareas in modal windows

reduce the right padding for .label-top and .label-none form components in modal windows
ISIS-537 Replace tabs with spaces. Remove unused methods.
ISIS-537 Revert a change to ToDoItem related to testing of @LabelAt positions committed by mistake
ISIS-537 Add an 'edit' icon for EntityPropertiesPanel
ISIS-537 Remove a div.clearfix to save some vertical space and for better alignment of the table view selector and the entity action links
ISIS-537 Add "registered trademark" to Powered by in the footer
ISIS-537 Improve the Bootstrap styling of ValuePage.html

https://trello.com/c/Ygt1zDSp/112-i-just-tested-todo-app-s-total-cost-functionality-and-found-out-that-the-valuepage-doesn-t-looks-very-pretty-at-the-moment
ISIS-939: simplified PersistenceMechanismInstallerAbstract and its subclasses, also PersistenceSessionFactoryDelegating, PersistenceSessionFactoryDelegate.

* Replaced PersistenceSessionFactoryDelegate#createPersistenceSession with #createObjectStore (other common functionality moved to PersistenceSessionFactoryDelegating).
* Don't pass ObjectAdapterFactory, AdapaterManagerSpi, OidGenerator into PersistenceSession; instead it can new these up (there is no variation in implementation nor state held in these components)
* Removed IsisObjectStoreLogger, IsisObjectStoreDelegating.
ISIS-939: more simplified of persistence sessions and object stores.

- deleted ObjectStoreSpi, just use ObjectStore (impl) directly;
- deleted AdapterManagerAbstract, not used
- deleted AdapterMapDelegator, not used
- for in-memory objectstore, renamed ObjectStorePersistedObjectsDefault (impl) to ObjectStorePersistedObjects (unextracted interface)
- renamed PersistenceSessionFactoryDelegate to ObjectStoreFactory
- renamed PersistenceSessionFactoryDelegating to PersistenceSessionFactory (unextracted interface)
- removed AdapterManagerSpi interface, just use AdapterManagerDefault directly instead.
- deleted AdpaterUtils, not used