[BLUEJ-1307] Improve Java code completion to be more like search

At the moment the Java code completion is quite straightforward; it prefix matches all currently visible methods. It lacks some features of the Stride code completion such as infix matching, compensation for typos, and search of available static methods (e.g. Greenfoot class).

We should revisit Java code completion, perhaps merging it with Stride code completion, or otherwise improve it with similar features.

Issue metadata

Issue type: Bug
Priority: Medium