improvements to ShareableMutex

- add some docs
- remove unnecessary null checks
- improve field name

Change-Id: I8299ec0d56ee5d903f05f2790f97f90ca00663cb
use SimpleReferenceObject in fpicker module

to replace hand-rolled version

Change-Id: I0c1cbf6b0e70106f4ecc5b579e09acc17045a44e
use SimpleReferenceObject in forms module

to replace hand-rolled version

Change-Id: Ic95f4dfd1ae5ab414c68c52ad58c738f4ac1d9d1
use SimpleReferenceObject in extensions module

to replace hand-rolled version

Change-Id: Ia983f5b87c55d8e5cce6f388e0f77077b6415745
use SimpleReferenceObject in dbaccess module

to replace hand-rolled version

Change-Id: Ie7b98c284d157521482b0f98915146133f32748e
use SimpleReferenceObject in connectivity module

to replace hand-rolled version

Change-Id: Ib415a6e78733277cbc1c0777d7263b65f404e6a4
use SimpleReferenceObject in extensions/update module

to replace hand-rolled version

Change-Id: I4cd74b3e95a61c32d3aa52646d654ce306791fae
fold dbaccess::IReference interface into the only place it is in use

Change-Id: I978a528e1da6f73c94549c2ced95b244ad5b6147
use SimpleReferenceObject in sdr::overlay::OverlayManager

to replace hand-rolled version

Change-Id: I3f47bf686ac07bba03acacace817767f2845af4f
use SimpleReferenceObject in StgPage

to replace hand-rolled version

Change-Id: I5301ef1df786b08b3c5d585a366d95722506f220
use SimpleReferenceObject in stoc module

to replace hand-rolled version

Change-Id: I30635aec81313e4e0d1b67b30c8992fd63bb1f67
use SimpleReferenceObject in vcl/osx module

to replace hand-rolled version

Change-Id: Idf3f2dd20bacd3cb3de64931027ef62d9116200f