Update process mapping calculation routine:

- Fix the bug with plane distribution.
- Simplify the mapping routine and make it distribution agnostic: node_cnt, task_cnt, task count per node and task ID's per node are enough to create a mapping, there is no need to have several cases for different distributions. 
- Move it to src/common/mapping.[c/h], so it can be used by several PMI plugins.

[Note] In case changes would be accepted autogen.sh should be rerunned.

The demonstration of plane distribution problem is provided in the following code:
https://www.dropbox.com/s/rloexlwcfffh0nt/proc_mapping_utils.tar.bz2?dl=0

I used OMPI pmi2 parser implementation. make and run pmap executable. The output will show results for packing/parsing block, cyclic and plane=2 distributions. The cyclic and block cases are OK but plane one is broken:
PLANE = 2 distribution:
pmi2: (vector,(0,4,4))
pmix: (vector,(0,4,2),(0,4,2) )
0: 	init: 0 1 8 9 
	pmi2: 0 1 2 3 
	pmix: 0 1 8 9 
1:	init: 2 3 10 11 
	pmi2: 0 1 2 3 
	pmix: 2 3 10 11 
2:	init: 4 5 12 13 
	pmi2: 4 5 6 7 
	pmix: 4 5 12 13 
3:	init: 6 7 14 15 
	pmi2: 4 5 6 7 
	pmix: 6 7 14 15