Deprecate base_kde_formula

[tlvince]

@adamv, @MikeMcQuaid, we're currently building homebrew-kde with the hope to get it under the Homebrew organisation.

Most KDE formulae share the same build depends/scaffolding, which has been generalised in base_kde_formula and extended in each formula, e.g.:

require File.join(File.dirname(__FILE__), 'base_kde_formula')

class Akonadi < BaseKdeFormula
  ...
end

What are your thoughts on this pattern? AFAICT, no other homebrew repo does this, but there maybe some merit to use it here.

[MikeMcQuaid]

I don't think it's a good idea, personally. The reason we don't do that is because it makes individual formulae harder to follow.

[adymo]

@MikeMcQuaid There's a lot of code in base_kde_formula dealing with cmake flags and installation prefixes. What do you think would be the right approach?

[MikeMcQuaid]

The main problem I believe is that these all install into the same prefix rather than individual Cellars. That alone I think makes this not very Homebrewy and I'd personally not want this as an official tap until that's sorted.

In terms of shared code I think they should just exist in every formula, personally. Formulae are not software, they are descriptions of a build process. If I cannot open a formula file and infer what the build process is they have failed at their job.

Another solution which may kill two birds with one stone would be having a single, monolithic KDE formula which allows enabling/disabling packages using options.