Tonel: sort class variables and pool alphabetically ...just like Pharo does. This minimizes noise in diffs / commits.

Write categories as symbol literals ...as Pharo does.

Handle removed methods in `#monticelloTimestamps_code`

Use `#monticelloPackageName` in favour of `#monticelloName` ...as the latter is actually used by the rest of the code and having two only asks for confusion (been there :-)

Make `ProjectDefinition >> #monticelloTimestamps_code` an extension in `stx:goodies/monticello` ...and convert it to use (not so) new annotation-based extension mechanism.

Update class category to match package name if it does not This is needed because in Squeak / Pharo world package membership is defined by (class) category prefix. This is soo annoying...

Revert part of 777d77ca96cf This commit reverts part of commit 777d77ca96cf ("Transform snapshot just before loading into / just after creating from"). In particular, it moves pre-write transformation to be done just before writing the package. This is to (restore) support for exporting to Tonel using custom exporter.

Ensure that class category matches package when writing Tonel ...otherwise Pharo gets confused and assigns class to different package!

Append filename to error when parsing Tonel file ...as a courtesy to the user. Makes debugging easier, especially after incorrect merge.

Tonel: only load files ending with `.class.st` and `.extension.st` This prevents tonel to load some git merge artifacts (line when in the middle of interactive rebase or similar).