Factored out backends of probing pop-ups from GetFstabEntry.

doc typo: the correct key is "mntops"
renamed check_options to Nfs::Options::validate
Added minorvers=1 for pNFS (FATE#312259).

factored out Nfs::Options::{get_nfs41,set_nfs41}
VERSION + .changes
Document which code in other projects determines the options

including links to git repos. clickable FTW!
doc comments, better constant names
Nfs::Options::validate: readability thru better names

...and "const", foreach
thx jreidinger!
Nfs::Options::validate: quote in error messages; more tests

test "Invalid" case
test simple=bogusvalue
Nfs::Options: factor out from_string, to_string
changelog: fixed misspelling; timestamp updated

still OK to change the changelog before merging
Merge pull request #6 from mvidner/Code-11-SP3

parallel NFS: pNFS aka NFS4.1. FATE#312259