Add ExecuteCallback to Misc.lua, and make code a bit prettier
Utils: create new UI element "NumericInput"

This is basically just an input field tailored for integers,
with buttons left and right to increase/decrease the value respectively.
Implement first configuration options for screen placement

Turbine-like buttons to revert changes, load defaults and accept new changes.
BuffIconWindow needs cleaner implementation to react to configuration changes.
Bump version to 0.2