Timestamps: proper support for temporal maps (client-side)

Right now the only supported data types are numbers and categories in the form of strings.

We need to support timestamps and give the proper Date/Time utils to work with them.

The WWI_Ships example is a good starting point since it is working thanks to a column which is the number of days since 1917 instead of using the timestamp column.

We need to define the syntax/style API first.

I imagine something like: torque($date, from: '15/01/1917', to: '1/01/1922', speed: '15 days'/'1 second', range: '10 days', trail: '10 days')

Where from and to are the start and end timestamps (should be optional, by default it should take the minimum and maximum timestamps of the dataset), speed is the simulated time that passes each real-time second of the simulation, in this case 15 days per second, range is the time duration in which the input is considered active (i.e. temporalSimulation returns 1), trail is the time duration in which the input is considered semiactive (i.e. temporalSimulation returns a number greater than 0 and less than 1).

The output of this function is (regarding the input $date) is:

Output
 ^
|1.66|
|1.33|
|1.0 |        ______
|0.66|       /      \
|0.33|      /        \
|0.0 | ____/          \____
=================================> Time

Note: I’ve used named arguments, IMO this improves clarity, but we haven’t implemented this yet.

[Jesus89]

I replaced moment.js by little maths with Date some time ago, saving half size of the Carto.js bundle: https://github.com/CartoDB/cartodb.js/pull/1981

[rochoa]

Literal timestamps should follow ISO 8601, as it would be easier to support time zones and adjusting that to the client configuration.