file organiser reassign_trials_denovo bug

[d1manson]

I have seen on skype, but not been able to reproduce the following bug:

When tetrode 7 is selected, the files for tetrode 8 of the first trial are incorrectly rendered as selected rather than than those of tet 7.

Perhaps this has something to do with having a very long list of trials.

There is also a bug where the active cut is not shown as being active. This is due to _reassign_trials_denovo (which is called when user does multiple file drops into page and when a drop includes orphaned cut files). This affects both last_used_cut for each tet_obj and selected_cut. This is definitely worth fixing.