ISIS-676: fix to edit/cancel/edit issue
ISIS-654: very minor tidy-up of code.
ISIS-691: improved null handling for drop-down lists

- for entity refs, if null, shouldn't default to showing the first in list
- for values (enums), should be able to set to null (in list, the blank line)
- get rid of clear link for entity refs, instead set by choosing from list, same as the value drop-down
ISIS-677: blob/clob panel fixes.

* display the filename
* stop using the CSS/javascript hack and rely on native <input type="file">
  - seemed to be the cause of the double input thing.
ISIS-692: removing flicker of choices drop-down
ISIS-684: moving quartz job delegate to JDO, so can reuse.

Also cosmetic tidy-up elsewhere.
ISIS-693: extensions in support of excel import/export

Specifically:
* RuntimeContext#bookmarkFor(Class,String)
* ViewModelFacet#memento(Object)
ISIS-694: mothballing the docbkx folders.