[autotools] removed unneeded Makefile.am
[linearelliptic.discretizations] moved to playground
[autotools] removed Makefile.am
[examples] moved and renamed some stuff
[cmake] update
[linearelliptic.discretizations.cg] moved
major refactor
* removed not working fv, swipdg and multiscale examples
* moved cg example back to linearelliptic
* updated linearelliptic problem
* added linearelliptic discrete problem
* added linearelliptic base discretization
* updated linearelliptic cg discretization