Adds a method classifier

- adds Helios command to classify unclassified methods
strat to implement chain of responsibility
Merge remote-tracking branch 'upstream/master' into classifier
Passes done over the classifier

- Introduces a `chain of responsibility` pattern
- Renames `execute` into `classify`
- Renames `classify` into `doClassify`
Gives focus on input in `HLRequestWidget`

- Extracts the superclass behavior of giving focus to the button
- Overrides this code in `HLRequestWidget` to prevent this behavior
- Gives focus to the input
additional comma and addAll: test for overlapping Sets
ifAbsentPut: tests

Array does not have at:ifAbsentPut:, ???
Push at:ifAbsentPut: up
Tests for comma in HashedCollection, allowing comma

Pharo has comma for Dictionaries.
Merge branch 'upstream' into at-ifabsentput-tests
Update API-CHANGES.txt
Update API-CHANGES.txt
Merge branch 'upstream' into allow-comma-for-hashedcollection
validation of --base-path only directories.
FileServer:checks --base-path but only warns on problem values
FileServer --base-path validation checks are async and console warn:
FileServer>>validateBasePath clean space stat parameter;used ifNil:ifNotNil on err; reformatted warning messages.
Rewrote AmberCli.st from IDE
Merge pull request #785 from herby/at-ifabsentput-tests

at:ifAbsentPut: tests, additional tests for Set
Removes HLReferencesModel >> allSelectors that was slowing down
references further searches