Merge branch 'master' into jed/ts-eimex

Sync to include Git conversion, PETSC_EXTERN, and minor API changes.

Conflicts:
src/ts/interface/tsregall.c

Commit after merge.

Hg-commit: a128a87f5736ccbab37df5d559616f8376f7026e

reorg of src/sys directory
directories that define objects now in the classes subdirectory
rename several confusing name directories

Hg-commit: b2612422c63ac4afe82112892d9efda808f3d601