Drop DoubleFloats dependency?

[oxinabox]

DoubleFloats has a fair few dependencies. Like SpecialFunctions, Polynomials, QuadMath etc. (including some like Intervals.jl which trigger a fairly high number of invalidations, thus making loading this slow). Removing it should speed up loading a fair bit.

It is only used for https://github.com/queryverse/TextParse.jl/blob/ced8d24743de7ee3c3c0a49074b9112b822de4cb/src/field.jl#L145-L164

Which in turn only needs:

• Creation
• Conversion to float
• Multiply
• Divide
• ^

We could port just those functions across. Or maybe there is another algorithm for x*10^y (integer x, y) that we can use that doesn't need it.