cmake variants: default option support

[Arniiiii]

Right now if use cmake-variants, you still is requested to choose among a lot of options, but there's no default option, though in cmake-variants we write it.

A possible solution: add the default option to the list from :CMakeSelectBuildType to position 1

Alternative solution: if entered no number, choose default.

Possible problems: checking if there's default for every choice.

[Civitasv]

Actually, you only need to select once, we support session save and load.

[Arniiiii]

Actually, you only need to select once, we support session save and load.

You are right about the capability.
Though, I'm about simplifying even further: if someone have to select something, he can press 0 or nothing to set default option. It will make redundant for developers to find that specific option among hundreds and thousands of options, if they just want default proposed by cmake-variants.* .

[Civitasv]

I've enabled default option, use the latest commit.

[Arniiiii]

It works! Great thanks to you!