Fix loadComponent to use basePath.

Prior it didn't use basePath and so didn't find Components
if the QML-files were not in the same directory as the html-
file (=> basePath was not ""). Instead it resetted basePath
to be always "". Now both is fixed.
Fix resolvePath to return "" if the filename is "".

If e.g. the source of an image is set to "", that means no
image should be loaded. But if the basePath was not "",
resolvePath used to return the basePath (something like
"qml/"). The concequence is an http-error trying to access
the base directory as an image. Now resolvePath resolves ""
always to "", resulting in the browser not trying to access
a not existing image anymore.
Call Component.onCompleted also for repeater-items

With this change Component.onCompleted will also be called
for elements that were dynamically created by a repeater
after the initial creation process.
Fix fatal mistake in last commit.

In the last commit I accidentally wrote this instead of self
with the consequence that adding an element in a repeater
was impossible after the initial creation-process, as
self.$completed was never set to true.
Fix repeater to set itself completed correctly.

Prior the repeater set itself completed after setting it's
default-values, so before applying the actual model. So the
property $completed did not have any effect at all.
Sorry for the badly tested code! (Now everything should be
working.)