Patch for database filtering in Connect to Server dialog

Hi all,

please find attached a small patch for pgadmin based on a personal need. On
our server we have approximately 400-500 databases that is a problem when
trying to select one from the drop down list of the "Connect to Server"
dialog when using the query tool. The list is huge and you have to scroll
down a lot. Also you may not know the actual database name but you want to
search based on a part of the name. As a solution, i have added a textbox
in the dialog which filters the available databases based on the user
input.

Please note that my C/C++ skills are very poor and it is the first time i
work with wxWidgets so feel free to rewrite the code or even drop the patch
in case you think this is not a general need.

Thank you,
Dimitris