Feature: string filtering for code completion [Patch attached]

[David Nolden]

Ah yeah, one missing:
test.n*something: Filter list for everything that contains "something"
in the name.

Another problem will be, that the filtering won't work properly in
"minimal" completion mode, as there we don't feed the return-type and
such stuff into the completion-model at all. We could solve this by
automatically re-starting a "manual" completion as soon as we
recognize the magic character and start the filtering.

I've also got an idea how the problem of the completion-model range
updates can we solved: We simply don't tell the models about anything
that is typed starting with the special character, so we keep the
completion-ranges for example at "test.".

Btw. I think this is a very useful feature.

Greetings, David