plfs: better container deletion

Defer container deletion until last moment so that if anything fails in the
middle, the container informantion remains.

Change-Id: I035d892b6e344ba5faa94b2184c5327153e84128
Implement small file mode for PLFS.

Small file aggregation mode can enable aggregation on both data
and metadata which can greatly improve the performance for small
IOs such as creating lots of files and appending data to them.
Merge pull request #1 from bergwolf/container_delete_for_qa

plfs: better container deletion
Merge pull request #169 from zhang-jingwang/small_file

Small file
fixed the plfs: prefix condition for the core library, added a function is_plfs_path that determines if a path would be inside a plfs mount, and renamed is_plfs_file to is_container_file (while isolating it to container_internals.cpp)
temporary fix for the statvfs warning we often see when linking against plfs, would like to get #define HAVE_CONFIG_H working, so far no luck, Also redid is_plfs_path to return 1 if True, 0 otherwise
fixed a comment in plfs.h about is_plfs_path
cleaned up .gitignore a bit, fixing patching now
re-added Makefile 'in' files for scripts/make_ad_plfs_patch
added mpich2 to .gitignore
Merge branch 'small_file_fix_paths' into cmake

Conflicts:
	Makefile.am
	configure.ac
	man/man5/plfsrc.5in
	src/Makefile.am
	tests/Makefile.am
small file mode is building with cmake, bug still exists with statvfs, and plfs_version
plfs_version works, statvfs works, create a config.h file from config.h.in for extra variables