Add button to ensure filtering is finished

[lehecht]

Closes #692.

Add a 'Test file query' button to enable volume cloning only after the filtering process is finished.

[mzur]

I think the original idea has to be refined a bit, as the UX is currently not good:

• Instead of replacing the "clone" button, the "test query" button should appear somewhere next to the query input field when "filter files" is checked. Perhaps you can find a solution that does not occupy too much additional space. The button should still be .btn-success.

• When "filter files" is checked and the query is unchecked/dirty, the "clone" button should be disabled with a title saying that the query has to be checked first.

• When "filter files" is unchecked, the "clone" button should be enabled again, even if the file query is unchecked/dirty.

• When the file query is checked/ok, the "test query" button can disappear.

[mzur]

Can you please move the "test query" button above the file pattern input field? It can still be .pull-right and maybe change it to .btn-xs. As it is now, it overflows to the checkboxes below and can sometimes not be clicked. Also, it's quite far away from the input and the relation is unclear.

Now if I initially click on "filter files", the "clone" button is still active. However, cloning with an empty file list should not be possible. Also if I enter a file pattern that turns up no files, the clone button should still be disabled.

If I change the file query but don't click on "test query", the clone button is correctly disabled. But if I now uncheck "filter files" and immediately check it again, the file pattern is still changed and does not match with the previous tested file list. Furthermore, the clone button is enabled now but it shouldn't, as there now is an untested file pattern.

[mzur]

Thanks! I've tweaked the button position and updated the clone button title texts one final time.