Added comment on why loops cannot be used directly on m_d->cacheJobs

• Fixed the problem that kazv cannot be closed when cached files

In D176#3265, @tusooa wrote:

test that if it is cancelled, the file will not be found on disk.

In D178#3268, @tusooa wrote:

How is it "less buggy"? What bug does it fix?

Add tests for KazvFile and KazvSaveFile

Rebase onto servant

• Delete redundant code

• Remove test code that delete local echo failed

• Delete trailing newline

Handle the case where find_if returns localEchoes.end(), and update related test

In D143#2771, @tusooa wrote:

otherwise looks good

• Use MockHelper and deepEqual for test

• Use eventId instead of timeline index

• Add test

• Use index instead of eventId, fix cant display local echo in confirm popup

• Distinguish between events and local echo, add tests
• rebase onto servant

• Fix a error arguments format

• Use eventId instead of eventView for signal deleteEventRequested

• Use component for delete event confirm popup
• Add event content for delete event confirm popup
• Fix test

Rebase onto servant