Fixed, Numeric textbox: incorrect character was treated as decimal separator character was used when using certain Windows regional settings.
Changed, Edit Things window: when applicable, the "Filter" textbox is now focused when opening the window.
Changed, Sector Effects browser window: when applicable, the "Filter" textbox is now focused when opening the window.
Changed, Edit Things window: when the "Filter" textbox is focused, pressing the "Down" key will now switch focus to the Things list.
Changed, Sector Effects Browser window: when the "Filter" textbox is focused, pressing the "Down" key will now switch focus to the Effects list.
Changed, Linedef Action Browser window: when the "Filter" textbox is focused, pressing the "Down" key will now switch focus to the Actions list.
Configurations, Doom map format thing flags: changed "Multiplayer" flag name to "Multiplayer only".
Fixed, Texture Browser Form: well, I broke "Tab" key functionality again (in previous commit)...
Maintenance: changed curly braces style to match DB2 one (hopefully not breaking anything in the process...).
Maintenance: changed private method names casing to match DB2 one.