Script window usability improvements

[NickDraper]

From Pascal:

I noticed a couple of things in the new python interface.
The tabs are a great idea but it always default to the first tab opened after having ran a routine. Even if it reports an error at a given line of another routine, it goes to the first one. This makes lots of extra clicking.
The pointer sometimes disappear for no reason.
If you do copy and paste from one tab to the next, you can have problems if you don' t unselect the block you copy from.
The default directory where it opens should be the one where a routines was last opened not the last directory open by anything (by having executed a LoadRaw routine for example). The data directory usually contains 100's of files and it has to be scanned before offering the possibility to open a routine whereas the routines directory only contains a few routines.

[NickDraper]

This issue was originally trac ticket 975