Split file elpa1.F90 into elpa1.F90 and elpa1_compute.F90
For automatic generation of documentation, the file elpa1.F90 has been splitted into two files, in order to have a lean, easy-to-understand user interface: elpa1.F90 the visible user functios, which provide the library calls. The usage is the same as always elpa1_compute.F90 all internal routines, which are used by ELPA1 and ELPA2, but which are never called by the user. These functions are now "hidden" in the module elpa1_compute, which is used by ELPA1 and ELPA2. The procedures in elpa1_compute.F90 are identical to the ones in elpa1.F90 before this split commit. The only -- but lot of -- changes are intendation.