Implement connection editing.

Add admin mode;
Replace the drivers control with a Wx::ComboBox;
Add new IO exceptions for Read/Write files and catch them;
Rename method controls_read to sub controls_read_frompage and refactor;
Rename method controls_write controls_write_onpage;
Remove duplicate get_control_by_name;
Move POD to the end of the files.

Because of the PodWeaver Dist::Zilla plugin, the line numbers in the
source and that reported on exceptions did not match.