Breaking change backlog

[LTLA]

• Turn the isometric helpers into proper interfaces with all template parameters at the class level. This provides the option to avoid repeated compilation of multiple realized templates for each template type.
• Remove the isometric make helpers, people need to specify almost all the template parameters manually anyway.
• Isometric helpers should have a way of specifying the expected dimensions of the matrix they are applied to, e.g., to ensure that the vectors are of the right length.
• Remove all default template arguments, people should stop being wimps.
• Replace default function arguments (e.g., in convert_to_sparse) with an Options class and make an overload that uses the default Options.
• All interface functions should now accept references instead of pointers, which is nicer for everyone.
• Remove the delayed bind/transpose helpers as we can just call the constructors directly.
• Add final to all subclass declarations.