Check integrity status

[sambo57u]

Using 4.1dev 25 Oct. Java 1.8.0_152, Linux x86_64.

When you choose to check integrity of a relatively large bib file (about 2000 entries) jabref appears like
it is hanging but after waiting for 30 seconds the check integrity window pops up. If I remember correctly
in the past there was a little message counter on the lower left border showing the progress of the check.
Without this the feeling is like it is hanging since no mouse action works during this time. It would be nice
to have that working message again.