Transform solution groups into target aggregates

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branch : makefile-groups
move solution's phony rule and project group rules generation in dedicated functions

--HG--
branch : makefile-groups
sort subgroup first in group target dependencies

--HG--
branch : makefile-groups
add tests related to solution groups handling in gmake action

--HG--
branch : makefile-groups
Merged in grizzlynyo/premake-dev/FatalCompileWarnings_v201x_fix (pull request #114)

"FatalCompileWarnings" flags had no effect in vs201x actions
Merged in mendsley/premake-dev/xbox360-imagexex (pull request #116)

Add support for custom title configuration files in xbox360 builds
Merged in neo2buha/premake-dev (pull request #117)

Use seed for hashing
Merged in noresources/premake-dev-ns/makefile-groups (pull request #112)

Transform solution groups into target aggregates in Makefiles (bis)