prevent NPE if session does not exist
readme update
Update cy.properties

Ychwanegu, cwtogi, cywiro a thacluso.
Merge pull request #510 from Cymrodor/patch-1

Update cy.properties
delete old read statuses by chunks in order to avoid large transactions
create a new transaction for each delete chunk
delete operation does not support limit. limit on select and delete afterwards
Merge remote-tracking branch 'upstream/master'
prevent unintentional entry list reset
Merge remote-tracking branch 'upstream/master'