Refactored kvocdoc::open to increase robustness.

Added unittests to test 6 exit paths from kvocdoc::open
, fileDNE, unreadableFile, lockedFile, unknownFormat, readerFailed
and success.

Changed 4 KError -> kWarn as they are app recoverable errors
, (filelock, unreadable file etc.).
This removes 4 hard crash conditions.

Refactored code to reduce exit paths to 3
: file does't exist, file locked and everything else.

Added dummyReader which generates its own fake files as heralds to
generate success and failure indcations to kvcodoc::open.

BUG:336780
FIXED-IN: 4.14