Feature/add remove factors

[j-or]

• Option added to enable/disable factors while also updating data points
• Data points are updated when adding/removing factors
• Data point names are updated when factor names are edited
• Deleting a numeric data point value now results in a blank entry instead of 0

[j-or]

When editing a factor you can change from continuous to discrete without getting any validation error.

Hmm, does this matter though? It converts the continuous value to a discrete one - which is what you chose to do.

[langdal]

When editing a factor you can change from continuous to discrete without getting any validation error.

Hmm, does this matter though? It converts the continuous value to a discrete one - which is what you chose to do.

Where are the numeric values converted between continuous and discrete? The min/max values in the variable definitions are converted when calculating the space parameter, not the individual data points it seems. This must also be a problem in the existing solution.