Custom Unit Converter Widget

Simple measurement converter widget. There is a possibility to add custom units in admin area and disable or delete units.

Here are the Measurements and units included as presets:
* Angle – units Degree, Gradian, Radian
* Area – units Acres, Hectares, Square centimeter, Square feet, square inch, square kilometer, square meters, square mile, square millimeter, square yard
* Length – meter, centimeter, millimeter, foot, inch, rod, yard, mile, nautical mile
* Temperature – Celsius, Fahrenheit, Kelvin
* Volume Fluid – fluid ounce UK, fluid ounce US, Gallon UK and US, Pint UK and US, liter, quart UK and US, milliliter
* Volume Solid – cubic centimeter, cubic meter, cubic feet, cubic inch, cubic yard
* Weight – gram, kilogram, ounce, pound, stone