added support for new snes algorithms
Merge branch 'develop' of https://github.com/feelpp/feelpp into develop
backend changes:
 - added support for new non-linear solvers from 3.4
 - added support for --{ksp,pc,snes}-view=true|false
@Trophime @cdaversin we can now pass other parameters to the list of Symbols
next steps : extend to matrices
@StephaneVeys arg by reference and not copy, please correct the other ones!
more functions
Merge branch 'develop' of https://github.com/feelpp/feelpp into develop