Cache OCCA kernels in PETSc examples makefile

[occa] PETSc example with ctx inout, qfdatasize & offsets

[occa] device from ressource, OpenCL TILE size tied to 1

Switch to include/ceed.h and lib/libceed.so directory structure

This gives the source directory a compatible directory layout with
the install directory, thus enabling a user to use either.

.gitignore for examples

PETSc implementation of BP1