0.6.1-0.6.6 Delete added in Nic, IpHistory, better device selection, fixes

Some forms got a delete button.
While also work is done on general delete form (mneu Edit, Delete..) where more information is show about the occurence of the record intended for deletion.

0.6.6
Forms:
Nic can be deleted if not used in any other records (e.g. ipHistory)
IpHistory can be deleted (to be able to delete nic).
Path can be deleted.

0.6.5: cables in Connect form can be sorted on record id, color, or length now.

0.6.4 : Connect form; if location selected, afterwards device category selection works in this location (instead of all).

0.6.3 Cable form: fix bug, show column with current value after save.

0.6.2 Connect form bug fix ip address in Nic record, and ip address in Nic form can be removed by entering 0 or space.

0.6.1 Ip address form got extra column with all ip addresses and device name if in use.