Filter `arp' doesn't work

[choll]

i.e. "arp" is a valid pcap filter but for some reason PP doesn't accept it.

Also need to add some error handling, if a filter doesn't work the filter sheet shouldn't just disappear, it should show an error.

[choll]

Improved the filter panel a lot, it now checks the input as the user is typing (instead of only when they switch focus to another UI element), and the apply button is disabled if an invalid filter is entered

[choll]

The arp filter not working was rather subtle, the filter was compiled with a null linktype, if ethernet is specified it accepts it

[choll]

Fix issue #21 and improve the filter setup sheet

→ <<cset 5d3e9e2adc5a>>