Feature: Premake generator

[SSE4]

closes #3693

uses premake generator from https://github.com/memsharded/conan-premake

Changelog: Feature: New premake generator incorporated to the Conan code base from the external generator at https://github.com/memsharded/conan-premake.

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• If the issue has missing info, explain the purpose/use case/pain/need that covers this Pull Request.
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[SSE4]

seems to be infrastructure failure
python: can't open file '.ci/jenkins/runner.py': [Errno 2] No such file or directory

[memsharded]

Looks good. Needs to be labeled as "experimental" in the docs, please do so.
Thanks!

[SSE4]

I've played a bit with it, and some thoughts:

• it's probably worth to add multi-configuration packages support, just like qmake has
• it also worth providing premake_multi generator in addition to the premake (same way as visual_studio_mutli and cmake_multi)
• finally, it might be worth providing conan_basic_setup function/macro to automatically set all flags

[danimtb]

I think those are good ideas and would be helpful for premake users. I will keep them open in an issue and see if there is more feedback from people using it whne the generator is released. WDYT @SSE4 ?

[SSE4]

yes, let's keep them for a while, until there is a real demand for them. I am not a premake user, so it's hard to judge for me.