Always use the dummy crendential while trying to determine the credentials

Otherwise the SHibbolethCredential may be set and it has hook to intercept 401

This should fix issue #1908
Propagator: Fix local file name clash detection.

Need to normalize the output of QFileInfo::canonicalFilePath() before
comparing to a server side path.
See https://bugreports.qt-project.org/browse/QTBUG-39622

This fixes #1998 and #1999
HTTPCreds: Do delete the WritePasswordJob to not leak memory.
Bump version to 1.6.2 rc2 plus Changelog
NSIS: ICU rebumped to 5.3 as per build service change
propagator_qnam: add debug output in cae the file changed localy

In order to debug https://github.com/owncloud/core/issues/9781
propagator_qnam: Limit the HTTP buffer size when downloading

Otherwise the buffer might fill up too quickly and get too large and consume
too much memory which could lead to crash in extreme cases

Should fix issue #1974
Merge remote-tracking branch 'origin/1.6' into il

Conflicts:
	VERSION.cmake