simplify/improve kw proposals code
very minor
fix exit position of module import proposal
filter out dupe proposals
Add model delta tests for use-site variance
Fix errors in model delta test samples

Currently, the errors don't affect the delta, but that's going to change
soon (see #1152).

Almost all the changes are changing formal toplevel functions to proper
functions (with the definition '{}' or '=> nothing;'); the only other
case is the test for annotation aliasing, which failed due to
ceylon/ceylon-spec#1081. (See also #1152.)
Detect error changes as model changes

See #1152.
Add tests for error model deltas

See #1152.
Fix #1154
Do the same as the backend model loader
show type args in doc hover
very minor
- much better presentation of search results
- include doc links in find references
fix rendering of Java signatures
navigation from java to ceylon binary archives
minor
fix search in binary archives
handle java variance
more big improvements to how searching handles archives
fix tree view results from archives