Add keyboard shortcuts to Clients list view: Ctrl-A, Ctrl-F and Del

Ctrl-A - Select All
Ctrl-F - Filter IP address
DEL - Close Socket

Also, use Begin/EndUpdate() calls to batch updates to the ListView in Timer
tick (no visible difference, but it's the right thing to do).

I don't know why C++Builder increased the TextHeight value of this form from
13 to 15, but doesn't seem to really matter (or at least, I couldn't tell).