Fix BackgroundParser destruction

Queue does that on its own, on destruction.

Ack'ed by Mirko
Fix odd-looking code
Fix initial cursor position when jumping around

Not sure why all of this was this complicated. This removal of code just
fixes the issue...
Fix porting bug

While at it, also normalize the types used in that function
DUChainLock: Code cleanup
Fix another 'destroyed locked QMutex' warning

I don't see why WaitForUpdate used mutexes and wait conditions at
all, there's no concurrent access to it.

Next step: Hide class from public interface, it's just used internally.
Fix crash

'buttonBox' param of createKMessageBox must not be null.
Use the IndexedString(QUrl) ctor

This actually fixes an issue with the kdev-go plugin
Minor: Cleanup code inside duchain.cpp
sublime: Fix position of context menu
Fix ProjectController::prettyFilePath

Broke during KUrl->QUrl port
Remove references of IGenericProjectManager

This interface got removed long time ago
Make F4 work again

Epic fail. I always thought that's just a regression in Frameworks.

BUG: 339124
Merge remote-tracking branch 'origin/1.7'
Minor: Simplify code
Don't start parse project job if there is nothing to parse.

ParseProjectJob kills itself when all files parsed, but if there is
nothing to parse it'll stuck forewer.

BUG: 339072
SVN_SILENT made messages (.desktop file)
PlaceholderItemModel: Fix crash when inserting data

QIdentityProxyModel (the base) reimplemented QAIM::sibling in Qt5, hence
we need to the same in order to not pass invalid data onto the base
class methods.
Use 'override' keyword where applicable
Rename welcomepageplugin -> kdevwelcomepage

Consistency++