Operation: Convert co-ordinate format

[j433866]

Adds a new operation to convert between geographical co-ordinate formats / projections (requested in #228 ).

It currently supports converting to/from:

• Degrees Minutes Seconds
• Degrees Decimal Minutes
• Decimal Degrees
• Geohash (Replaces the To/From Geohash operations)
• Military Grid Reference System
• Ordnance Survey National Grid
• Universal Transverse Mercator (UTM)

In the future, more formats / projections could be added, and I'm working on getting an operation working to display co-ordinates on a map.

[n1474335]

Excellent work again.

I've changed a few large if/else chains to switch statements. JavaScript supports switch statements on strings, unlike Python, so I prefer to use them when there are a reasonable number of cases as it makes the code a little more readable.

I'd also recommend you take a look at ternary conditionals as they can reduce the need for so many nested if statements. It's always a balance between making the code a bit more compact but keeping it readable. I think in these cases, ternary statements are just as readable and help to reduce the brace armageddon!